Thanks for visiting my vintage Hamilton watch blog. I like to restore US-made Hamilton wrist watches back to their original glory and share my experiences with other enthusiasts. Use the "Search" space below if you know what model you're looking for. Feel free to leave polite comments or questions in the spaces provided. Also check out my "watches for sale" on my Etsy site - the link is on the right, just below.

Saturday, December 1, 2018

1935 Hamilton Fairchild Gun Camera Watch (aka "Bomb Timer")

 - 700 -

This post marks my 700th model!  I like to mark my 100th milestones with something special and I recently came upon something that fits that bill in spades.

The model is often erroneously referred to as a "Bomb Timer" but in truth it has nothing to do with that.  In fact, the model is actually a timer for Fairchild aerial gun simulators! It was introduced in 1935 and produced through 1938.  There are several variations based on the dial and movement inside.

In a nutshell, the watch was part of the Fairchild Type CG-16 Camera Machine Gun system that was either mounted in a machine gun or on the wings to represent a fixed wing-mounted machine gun.  Analysis of the resulting movie film recorded along with the elapsed time allowed estimation of the accuracy of the "shots" fired.

If you click on the photos below you should get a larger version that's easier to read.

In terms of the variations, the initial watches were produced in 1935 using the 980A movement, the same movement used in the Seckron doctor's watch.

405 watches were made with the D22 dial plus another 416 with the the D23 dial over the 1935 and 1936 period.  From then on the regular 980 movement was used and the D37 dial and D38 were used with 1,709 and 995 units produced, respectively.  So if you do the math, around 3,500 units were produced from 1935 to 1938, priced at $20 a piece.

How do you know which is which?  Looking at the dial prints, let's first look at the D19 dial used for the initial Seckron.  It has two registers, one for the hour and minute hands and the other for a large seconds hand.  You can see why this would have been helpful for people in the medical profession.

The D22 dial is very similar to the D19 with the crown on the side by the 3 but the shape of the hour and minute register is different.

 The D23 dial is very similar but notice the 12 is on the side near the crown.

In 1936 when the plain 980 movement was used, the D37 dial had the 12 near the crown and the hour and minute register shifted into the center of the movement, overlapping the second hand.

Finally the D38 version is the same as the D37 but the 12 is moved so the 3 is on the crown-side.

Armed with that information, if you see a "bomb timer" for sale you will be able to identify what version it is.

The other interesting fact about the model is it had a "hack" mechanism and could be stopped by pushing on a button so the watch could be stopped and started again.

Although the watch is sometimes modified to be fitted with a strap, it wasn't originally intended to be used like that.

I recently landed a Gun Camera Watch on eBay and I was not going to lose out on it - they very rarely come up for sale.  This one came looking fairly original and other than the goofy crown, it looks like a very authentic D37.

The second hand came with it but it wasn't installed.  Also I had to repaint it white.

The case back looks like it may have had a strap installed at some point.

Notice the hole on the side - that's where the rod for the push button hack mechanism would have been.  It looks like it was removed in order to install a strap.  Oh well... I'd rather have half a loaf of bread than no bread at all.

The dial appears to be original and shows some scars from past use.

The movement behind the dial is from 1947, based on the serial number.  It's running but could stand a trip to the spa.  The crown on the stem is obviously a replacement.

The case is made by Keystone.  My thumb is on the side where the hack mechanism would be.

Part of the hack mechanism is still there but there would have been a strip of wire extending from it that bent inward to stop the balance if you activated it.

The purchase included another movement and based on the split set bridge / yoke I can immediately tell you that it's a very early 980 movement.

Based on the serial number, this movement dates to 1937 and is totally correct for the watch.  Unfortunately it is frozen solid.  Maybe a good cleaning will do the trick... let's find out.

I was only able to get three bridge screws removed... the balance cock and on the barrel bridge.  The other three and the pallet fork are locked on TIGHT.  I will need to soak them with penetrating oil and cross my fingers.

Progress... I was able to remove the pallet fork and the barrel bridge so those parts could be removed. I can see the stem is broken off and part of it is still in the winding pinion and clutch.

Since the barrel is removed I can check out the mainspring.  I'd give myself a .05% chance that this spring is still usable.

As I suspected, the mainspring is set and will need to be replaced.  No surprise there.

The broken stem is now loose and ready to come out.

In addition to the broken stem, I also found some wire inside the movement.  Is it from the hack mechanism?  I wonder...

One screw left to go.  I soak and tap the screw with a screwdriver and hammer.

With a little effort, I can get the wheels to turn.  The 4th wheel has a bit of corrosion... that probably explains why it was locked up.

Finally!  The last bridge screw is out.  Now I should be able to clean everything.

I've seen worse.

8 minutes in the ultrasonic on wash and then two rinse cycles should clean the parts nicely.

I have a 5.5mm crown and a 6mm crown... I think I will go with the larger option.

Out of curiosity I removed the hack mechanism.  I can see where the wire must have been braised on.

Everything is cleaned and ready to be reassembled... wish me luck.

A fresh white alloy Dynavar mainspring is definitely a good choice for powering the watch.

Without the pallet fork I can see that all four wheels spin easily.  That's a good sign.

Okay, the movement is running but I don't like the motion.

Sure enough, the timer agrees with me.  Something is holding the motion back.

A little fiddling here and there and I eventually get the watch to run decently, but fast.

Getting warmer but since I have the 1947 movement, why not try that balance?  It has an Elinvar Extra hairspring too, which is better than the Elinvar spring used in earlier movements.

We have a winner!

I found out the source of the broken wire - it's from the yoke spring.  You can see the broken section compared with a whole spring.  So I will have to replace it.

It goes right next to yoke.  When you pull the crown, the stem moves the set lever and pushes on the yoke in order to shift the clutch wheel into the time-setting position.  When the crown is pushed back in the yoke spring pushes the yoke and clutch wheel back to the winding position.

I need to trim a new stem to the appropriate length so the crown will be next to the case.

Ta da!  I am delighted with how this project turned out.  The newly painted second hand is a little whiter but that's mostly due to my light tent and bright white light.  This watch looks great.  It no longer hacks but if it was to go on a strap it wouldn't be "hackable" anyway.  C'est la vie, it was a great find just the same.

How's that for a 700th post?  Less than 400 more watches to go!


  1. That's an amazing 700th post. Congratulations & keep up the good work!

  2. Thanks for a great and informative post. I have a D23 dial but my crystal is cracked and broken. Would a Seckron crystal be the correct replacement? Also, my watch will not start running until fully wound. Would you like to repair another Bomb Timer? IF yes, how do I contact you? Thanks for your time.

  3. I see Federal and Watch-Craft regular crystal and Rock-Craft thick replacement crystal for Seckron (1935) or Seckron B (1940). Would one of these be a correct replacement? Thanks again for your time.

  4. Or should I stick with NOS Hamilton? Is there a difference?
    What would you recommend? Would you have the correct crystal in stock? Thanks again.

    1. I recommend you measure the case and purchase a crystal will the correct measurements. Brand doesn't matter. No, I don't have one.

  5. Terrific! Thank you. It's like reading a good short story.