I have had something occur that I thought may interest you Guys - esp. the Newbies, like myself...
I purchased a 1917 Burlington (by Illinois) 12s 21J Pocket Watch that neeeded some work, including a new mainspring. When it arrived, I was very pleased, especially with the condition of the case. Like a number of you, I believe that a lot of the high quality 12s P/Watches are well underpriced for their performance and finish!

It all needed a good clean...much better now!

Just LOVE the Inscription on the inside of the Burlington cases!!

So fully disassembled movement and cleaned in my little Ultrasolic machine with L&R Fluids. Carefully inspected -THANKS Chris Abell for the checklist! Fitted new M/S and dipped H/Spring. Assembled movement - started up straight away...
Re-fitted to case - keeping great time straight up! THIS ONE LOOKS LIKE A KEEPER!!
So took it out for a walk (on my 1890 Simmons Chain) - No probs. Time right on....
The next day FOUND HAD STOPPED DURING THE NIGHT!! Upon careful inspection, found that there was no power to the Fork! Pulled the Balance, and put aside. Removed the Escape/4th Wheel Bridge:
OUT FELL A TIMING SCREW!! Looked at the Balance - sure enough one missing! Just as well I did not try to turn the wheels with the screw stuck in there!!
The screw on the opposite side was loose too! The thread fit was not really great, but they did up again OK.
CHRIS ABELL - Might have something to add to your venerable Check List : Check Balance Timing Screws for tightness.
David A : You can list this in Watch Repair Questions & Answers, if you deem it suitable.
SO : Did the Balance Screws come loose during the Ultrasonic cleaning?? Were they already loose? Did they come loose from the 'walking motion' of taking it out for a walk???
Cheers from the Aussie

Hi Philip,

Good to hear the list worked, I also have a secret list of about 1000 things that people do to watches that you would never expect and it grows daily. The screw should be firm as you a say a good idea to check during disassembly I have never had one that was correctly fitted come loose during of a correct type ultrasonic cleaning . (maybe note 1001 industrial ultrasonic ) what happens is people will cut the screws away trying to adjust timing and take out the thread also/stack a pile of washers and strip thread/wrong screw/glue them in with super glue and breaks down in tank (and many other parts glued together), the list goes on you think of it and it can be done it has been. Yesterday I was working on two high grade watches that someone had filed the heads down and off at wedge in a attempt to poise or time, damage done forever, then realizing there mistake stack timing washer everywhere to reverse it, what a mess, early this week I removed 20 minutes of timing washers to get back to a start point and correct the original problem, I was doubting my timing machine at that point and checked that against another watch!
While we touch on this I have never had any part damaged by the ultrasonic cleaning action (I use the Tempo machines fully automated they have combined alternating rotation and a powerful ultrasonic cleaning) often people will comment and even justifying by saying a watchmaker told them of the explosive power of a ultrasonic! that roller jewel, or jewels get damaged using a ultra-sonic and blame the machine, when if fact the shellac has broken down or poor past work, damaged parts being put in, again glue dissolving, dial screws not tightened prior to cleaning home made aggressive cleaning solutions etc etc lead to blaming of the ultrasonic.

Phillip, I totally agree with you about the unsung value of these fine 12 size movements. Yours is an escellent example of fine craftsmanship and execustion.

I believe the great influence of 16 and 18s "official" and "approved" railroad watches are all that can give substance to the hundreds of thousands of Hamilton 992's that sell for 5 - 10 times what collectors will respectfully pay for a fine and less prolific piece like yours.

The loose balance screws you had could be "mean time" screws (usually they have a longer thread than normal Balance screws) which have loosened up from readjustment over the life of the watch. When I run into these, I lightly flatten the threads to get them to be a little tighter. Many of these are solid gold so you really have to experiment with hos to do that.

Thanks Chris for the insight to even more things that can cause 'operational' problems !!
I should have included a pic of the Balance at rest, David - it has only two heavy timing screws. (Not like say the hamilton 12s which has 4 thinner headed ones) The ones next to the 'timimg' screws were the ones that had the problem...
Appreciate your thoughts re. 12s Pocket watches -:: But don't tell anyone - can not afford to have the prices rise too much!
Have a couple of Hampton ones which are also great to carry...
Cheers from the Aussie

The 12 size watches are excellent value indeed and will often, if in good condition and un-tampered with time out as well as any 16 size RR watch, look out for Hamilton 918, 920, 922, and not to forgot the 10 size also 917, 921, 923, often can be found in gold cases, even considering the gold case value you maybe able to get one for less than a 16 RR watch. I just got in a stunning (or will be once serviced) a 23j Lord Elgin in solid white 14K gold the finish in like new