Digitally Curious - A Vintage LCD Watch Blog

Digitally Curious - A Vintage LCD Watch Blog

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  • Wednesday, February 25th, 2009 - 1:46 pm
  • Casio 79QS-39 [79] Universal Calendar

  • Ah time to return to my roots. Here's another cool one from Casio's 1980 lineup.

    Too close? :)

    It's the famous Universal Calendar watch, model 79QS-39 with module 79. This watch was released in many varieties.
    79QS-39 -chrome plated w/ stainless snap-back with blue or black accents
    79QGS-39 -gold plated w/ stainless snap-back with brown accents
    79QS-51 -stainless steel screwback with blue or black accents
    79QS-53 -stainless steel screwback with blue accents

    Then, some time later Casio re-introduced this model as the UC-50W. I'm not sure how many varieties there were, but the one I've seen is a all stainless steel snapback.

    ***There is slight confusion about the history of this watch. Casio actually made a similar calendar display watch BEFORE they made the "universal calendar" models. But these Universal Calendar models were much more aggressively advertised. So when collectors talk about a Casio calendar watch they are usually talking about this watch.

    Here are several shots showing the watch's profile. It is a pretty thin watch, despite having a dual-layer LCD.

    In regular timekeeping mode, the watch just looks like any other watch. It has a nice big display with nice big digits. Very easy to read. In this mode, the date is shown on the top right.

    And of course there is the stopwatch and alarm modes. While the alarm is just a regular beep-beep, this alarm is equipped with 10 adjustable pitches!

    By the way, the stopwatch display is a bit weird on this watch. You would expect the two small numbers to show the 1/100 seconds. But instead, the stopwatch shows the hour, minute and second on the bottom row. The small number on the top right shows the 1/10th second. What does that mean? This watch does not have a 1/100 second stopwatch, despite having more than enough LCD space to show it. So in that last picture above, the time is 7.4 seconds.

    But the real feature of this watch is not its alarm or stopwatch. With a push of a button, you can see today's date (Shown is Tuesday, Feb 19th, 2009):

    Press the button again, and you see the entire monthly calendar! Wow!

    Not only that, you can scroll through the calendar forwards and backwards. You can scroll all the way forward to the year 2099, something that Casio tried very hard to market.

    But here's the catch. While you can SEE (scroll to) the calendar from 1930 to 2099, you can only SET the date from 1970 to 2029. So effectively, the watch becomes useless after the year 2029. :( And, since you have to scroll month-by-month, it takes a while (many many button pushes) to see the 2099 calendar.

    By now you may have noticed one more thing: the dates on the calendar display do not move around. Instead, a little marker on the top shows the "Sunday" position to give you a point of reference.

    Here's one thing I bet you didn't notice! The small digits on the top right are a little funny looking, aren't they? I didn't notice this until I started writing this article.

    The middle segment in that 9 looks.. pinched! This is because those digits are also used to display the date and alarm mode. Casio had to slightly "pinch" the middle segment to make room for the extra segments in that area.

    This is what the module looks like without the case. This is my spare module and you can see that it has flaw in the LCD. You can also see that the calendar grid is painted directly onto the reflector plate of the LCD.

    That little hole on the right is supposed to house a tiny spring, which makes contact with the alarm speaker on the case's front glass. Like other early Casio modules, things are held together with screws. Casio quickly moved away from this design in the 80's, and nowadays most Casio modules are held together using strategically placed plastic/metal tabs.

    Cautions when buying vintage watches with chrome plating:

    Chrome plated watches, especially with lots of wear and/or improper storage, will rust. More accurately, the chrome plating will corrode, exposing the underlying metal and then cause pitting, leaving tiny craters on the surface.

    Why does this happen? It has to do with some electrochemical science that I won't bore you with here. (Look up "pitting corrosion" on wikipedia.) Suffice to say, pitting generally occurs when you have non-uniform corrosion. Cr is corrosion resistant, whereas base metal is not. Therefore, if ANY part of the base metal becomes exposed, the less resistant part will corrode very fast--faster than it would have if it was left to rust by itself. The corrosion process will also localize and create pits. Chloride (naturally found everywhere, especially in saltwater) will greatly accelerate this process, so if you ever use a Cr plated watch near the ocean, wash it with water immediately.

    Putting Cr with base metal is an absolute nightmare in terms of pitting. Granted, electrochemistry was not a big field in 1970's but I am not sure which genius thought that chrome plated metal was a good idea.

    Gold plated base metal can pit as well, but not nearly as fast as the Cr plated ones. Also, Cr plating on plastic will not pit, as plastic can't pit. In fact, because the pitting process is electrochemical, Cr plating on any non-conductive surface will not pit.

    Here is a real life example of Cr plated base metal watches. Below I show three 79QS-39 watches. Why do I have 3? That's a long story. ;)

    You can see that the first one has very shallow pits, and is in good shape overall. The second one is slightly worse, with more aggressive pitting. The third one actually has a lot of general corrosion where a lot of the underlying base metal has corroded away. This process probably occured after many small pits formed. The insidious thing about pitting is that you can have massive pitting even when the rest of the surface is intact.

    So when looking at these old Cr plated watches, make sure you give it a thorough look from every angle. Just because the front is clean doesn't mean the back will be clean too.


    By the way, this watch is now in Colorado. I traded it with a fellow collector for something very special. :)

    Next up, the AX-510!

  • Filed under: watch
  • Comments!
  • » Hello!
    Looking Images of the manual
    Module 79
    Greetings from Argentina
  • by: C├ęsar, submitted Wednesday, January 12th, 2011 - 9:44 am
  • » I have one in pretty good condition and was wondering what it might be worth.
  • by: Jaye, submitted Monday, March 14th, 2011 - 11:03 pm
  • » Where can I find a manual for this watch? Or, if it's easier, how do I set the date on the date (not calendar) screen? Mine is off a day (perhaps due to leap year not being correctly calculated this year), eg. today is Tuesday April 3. My watch thinks it's Wednesday. Pushing the indented "Adjust" button on the upper left side of the watch edge does nothing in this mode. It works OK for changing the time display. Perhaps it isn't intended to work on the date display? That would be unfortunate.
  • by: Dennis, submitted Tuesday, April 3rd, 2012 - 2:52 pm
  • » Hello there! I don't know if you've abandoned this site completely (which would be a shame), but I'll still try an post my question:

    The crystal on this one -- real glass?

    Thank you!
  • by: Timefly, submitted Tuesday, October 2nd, 2012 - 3:48 pm
  • » I saw this Universal calendar watch during the year 1982-83 when I was in 10th standard.One of my friend was having this watch. Really amazing. I would like to know whether CASIO company still makes this model? would like to buy one.
  • by: nilesh, submitted Monday, December 2nd, 2013 - 5:50 am
  • » Found my old Casio and replaced the battery but can't get it to change functions. I can get the seconds to flash for change and the date and calander to appear but it won't flash for change on any function but the seconds when I click on the adjust function. Any suggestions?
  • by: Ron, submitted Thursday, July 10th, 2014 - 3:34 pm
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