Casio TM-100 Transmitter Watch

In 1987, Casio released the TM-100, a most unusual digital watch. On the surface, it appears to be a normal time-telling model but deep inside Casio embedded circuitry to transmit audio signals. Flip the little lever above the display, raise the telescopic antenna and speak or play music into the little microphone and the TM-100 will broadcast the audio to nearby radios! A tiny tuning knob allows you to calibrate the preferred frequency on the FM band (specifically, the Japanese FM band which is 76-90MHz and a portion of the US FM band, 87.5-108MHz). The case is all plastic and it requires two batteries, one for the timekeeping feature and one for the transmitter.

To us, the TM-100 is partially shrouded in mystery. We have never seen it advertised and it is a relatively uncommon watch. The transmitter feature was never included in any other model. We know of a few gadgets sold in Japan (the birthplace of karaoke!) included a transmitter but no wristwatch. Does anyone have any information?

Make: Casio
Year of Manufacture: 1987
Model Number: TM-100
Module Number: 661

Our friend akitaishi posted a couple of very cool videos of his Casio TM-100 in action! Witness a most interesting marriage of technologies: the source is an iPod with digital audio files, playing into the Casio TM-100 and broadcast over FM into a classic ’80s boombox.

1980 Casio GM-10 Game Watch

In the early 1980s, we couldn’t get enough video games. We played them at the arcade, in restaurants, shopping malls and grocery stores, at home on the computer or on the TV, in handheld form and yes, even on a wristwatch. The game watch like this Casio Game-10 was the bane of every school teacher. But for students, this small, hidden pleasure made a dull lecture almost bearable.

The GM-10 was Casio’s earliest animated game watch. Using the two pushers on the right, you maneuver your ship and fire missiles to fend an alien attack. The Game-10 also features a chronograph and alarm. This model is usually black, the beige version offered here is an unusual color variation. Beautiful condition and a genuine “old stock” Casio band has been fitted to make this look perfect.

Make: Casio
Year of Manufacture: 1980
Model Number: GM-10 (“Game-10″)
Module Number: 165

$499 USD plus shipping. Payment accepted via Google Checkout or credit card. In person pickup available if you’re near Atlanta. Contact us for more information.

1983 Casio CD-40, The First Data Bank Calculator Watch

Rewind to 1983 and you could have purchased this gem in your local department store.  The marvelous CD-40, a 24-button multi-function watch, the first of its kind.  What does it do…calculator?  Check.  Alarm? Yep.  Stopwatch.  Hourly chime.  And Casio’s Data Bank feature.  Think of it as a note pad on your wrist.  Not so high tech today, but this watch is almost thirty years old!  Plastic case, genuine signed resin strap.  Works perfectly.

Make: Casio
Year of Manufacture: 1983
Model Number: CD-40
Module Number: 246

$169 USD plus shipping. Payment accepted via Google Checkout or credit card. In person pickup available if you’re near Atlanta. Contact us for more information.

1980 Pulsar Calculator Watch

We discovered a two-tone all-metal, made in Japan calculator wristwatch on the shelf in a midtown Manhattan electronics store recently, literally gathering dust. As iPhone and digital camera accessories moved briskly from adjacent shelves and into shoppers’ hands, we realized the public had dismissed yesterday’s technological marvels like this one.

Fortunately, with new batteries this Pulsar (made by Seiko) is running like new. All functions work perfectly: alarm, stopwatch, calculator and the display that illuminates by a tiny bulb. Selectively pushing The tiny buttons poses a challenge for the average finger, but Seiko planned for that: a small stylus ejects from the bracelet clasp, perfectly designed for the tiny controls.

Make: Pulsar (movement by Seiko)
Year of Manufacture: 1980
Model Number: Y739-5019

1978 Digital LCD Citizen Scientific Calculator Watch 49-9421 cal. 9140A

1978 Citizen Scientific Calculator Watch from Japan with Box

Behold, we present to the Citizen scientific calculator watch, the master of “nerd watches”. The two-row display shows time, date up top and an eight-digit display for calculating below. Forty buttons surround the dial, many serving two functions. The display can be illuminated with the push of a button too. Includes signed Citizen display box. To those who prefer silvertone/stainless steel, sadly this model was only offered in goldtone.

Make: Citizen
Year of Manufacture: 1978
Model Number: 49-9421
Caliber Number: 9140A

New In Box 1979 Seiko C359 Calculator Watch

Dead Stock Seiko C359 Calculator Watch Complete with Stylus, Instructions & Box

Seiko’s second calculator watch, a beautiful stainless steel model from 1979. Check out the tiny keypad beneath the display. You’ll need stylus, pen/pencil or very tiny fingers to use it. The grille to the left is for the alarm. The LCD shows time, day of week and date. A light illuminates the display for calculating in stealth during night missions or during blackouts. Made in Japan, this one includes the original box, hang tag, signed stylus and instruction manual. Brand new battery, all functions are working (calculator, light, alarm and time functions). The display is perfect, no discoloration or fading.

Nerd Watch Museum Update

After a 10-year run of our Nerd Watch Museum we’ve decided to upgrade. The new format allows for easier, faster content additions and better engagement from you. For posterity’s sake, we’ll preserve a copy of the original landing page.

Welcome to PocketCalculatorShow.com’s Nerd Watch Museum. Our collection spans hundreds of models, dozens of manufacturers and infinite gadgetry. Since your hosts are of the LCD generation, rather than LED, liquid crystal display models have been the focus of our collecting. Many LCD timepieces played an important role in the evolution of digital wristwear, and we are striving to present as many as possible in our virtual museum. If you’ve got an unusual model that would make a great addition, please let us know! We’ve got many available for purchase too, so please check out our For Sale page.

Nerd Watch Fun Part Two!


Great Scott! Back to the Future character Doc Brown’s watch of choice is the Seiko A826 Training Timer from 1983. The functions are controlled by a rotating bezel and a wired trigger that attaches to your finger. Can you think of a more fitting watch for the inventor of time travel?


If you look closely, you’ll notice Doc Brown is wearing a second watch–a silvertone calculator model on his other wrist. Could be an Armitron, Nelsonic or Advance…any ideas?


In Back to the Future, Michael J. Fox’s character Marty McFly is also wearing a calculator watch. After analyzing the DVD and some catalogs from the period, we have high confidence that the time-travelling slacker is sporting a Casio CA-50.


A few Seiko watches made an appearance in the 1986 film Aliens. Sigourney Weaver/Ellen Ripley is wearing a stainless steel A728-7000 Speedmaster and the android Bishop is equipped with the matte black A728-6000 Speedmaster. But if you take a close look at the Marines, you’ll see each one is wearing a black Seiko S234-5000 Pulsemeter.


We receive many requests asking to identify Michael Knight’s wrist communicator, the radio watch David Hasselhoff used to talk to his four-wheeled partner KITT on the ’80s hit drama Knight Rider. The watch, cosmetically enhanced for the show is a Hong Kong made LCD model sold under a variety of brand names (Nelsonic, Gala, Advance, Quasatron, etc.). But this gadget watch is pretty neat in its own right–it has a built-in AM radio. Plug a set of headphones into the hole on the left and tune the dial…we recall this one being a great diversion in our junior high school Algebra class.


In the 1983 film Blue Thunder, Roy Scheider’s character Frank Murphy is an ace police chopper pilot on edge. He keeps his sanity with a wristwatch…a Casio AA-85 to be precise.


Nobel Prize-winning American economist Milton Friedman championed the idea of laissez-faire capitalism. He is considered one of the most influential intellectuals of the 20th century. His watch of choice? A Casio C-80 or C-90 calculator model.

Nerd Watch Museum: Game Watches


Casio CA-901 Multi-function calc with game mode, c. 1981.


Casio CA-90 Black plastic multi-function calculator watch with game, c. 1982.


Alba Y827 Seiko-made watch with “Gunfight” and “Slot Machine” games; 1981.


Casio GM-10 Casio’s earliest “video” game watch. c. 1980.


Casio GM-30 1980 Sub vs. Ship game, alarm/chrono.


Casio GG-9 Golf Game Watch; c. 1984.


GCE Arcade-Time Amazing multi-game & alarm w/ joystick.


Chips Ahoy! Game Watch Chocolate Chip Cookie Star Trek Promo Space Attack Clone.


DataTime Monte Carlo Monte Carlo w/ 21, Blackjack & Dice games. 1970s.


Alba Y765 Mamagon “Dragon Lady” game watch.


Alba Y822 Baseball Voice & Game. c. 1983.

Nerd Watch Museum: Nerd Watches, Part One


Casiotron Calendar 200 1978; 200 Year Calendar.


Casio DW-5000 The initial model for a long-running and popular series by Casio, 1983.


Casio Melody Multi-melody alarm, 11 Popular Songs, c. 1980.


Casio M-1230 Silvertone version of plastic Melody model.


Casio 79QS 1980 Universal Calendar, adjustable frequency alarm.


Casio AX-250 1980 Techy Digi-Ana Package w/ melody alarm/chime, Full Calendar.


Casio M-15 Later Casio pop song Melody Edition, c. 1984.


Casio W-400 aka Marlin Pre-G-Shock Mariner Model, c. 1980.


Casiotron 52QGS Casio Dress Watch Chronograph; $100, c. 1978.


Casio AA-85 LCD displayed hands, multi-alarm, c. 1980.


Casiotron X-1 Earliest multi-function Casiotron; World Time, c. 1977.


Casio 56QS Casio LCD Analog Timer/Chrono/Dual-Time, c. 1979.


Casiotron R-12 1976 Slim Dress Digital Casio.


Casio LM-5 Casio Yogi Bear Kids LCD; one of several using same module, c. 1981.


Casiotron ST Slim “Slim” designation Despite 11mm Case, c. 1978.


Casio TM-100 Casio FM Voice Transmitter Tx ~60ft @ 88-108 mHz, Alarm/Chrono, c. 1987.


Casio F-100 First 1/100″ Chronograph @ $25 price point and Casio’s earliest plastic watch, c. 1977.


Casio AE-11W Casio AE-11 Successful 50M model kept LCAs alive, c. 1987.


Casio W-23 Pre-G 50M model with Marlin graphic, c. 1980.


Casio AE-80 All-LCD marvel from the Master, c. 1985.


Casio TRN-100 Neat Casiotron Re-Issue; c. 1998.


Casio AA-86 Cool LCD w/ hands with dressy dial.


Casio TE-2500 Dictionary Translator Watch; c. 1983.


Casio CGW-91 Cosmo-Phase Displays Solar System; c. 1990.


Casio TSR-100 Thermo-Scanner; Hi-Tech directional temperature sensor; 1993.


Casio Moon Graph Another Astronomy Casio, Displays Moon Phases; 1990.


Casio T-2000 Japan release of the Dictionary-Translator Watch; c. 1983.


Casio RKA-5003 “Rookie” Adventure Club release of the Moon Graph for Japan market; 1990.