I recently repaired a Seth Thomas Mark I Navy Deck Clock. The works were actually in pretty good shape and only needed a cleaning, except for the hairspring, which was broken. The clock actually still ran because the free end of the hairspring was stuck in the regulator pins, but it ran erratically, as could be expected. After much trial-and-error I was able to find a hairspring that I could vibrate accurately and the clock is keeping fairly good time, except it runs slightly fast with a full winding, a slightly slow at the end of the week. By slightly fast I mean, in the first three days it will run about 30 seconds fast, total, then gradually slow down to where it's correct again at the end of the week. The hairspring and balance seem to be in great shape and there were no issues with the balance after I cleaned-up the regulator pins. Can anyone offer a suggestion as to why the rate varies? Or, is this a pretty acceptable result for this clock? Thanks very much for reading!

GREETINGS RICHARD, THE CLOCK SHOULD RUN CLOSER TO THE TRUTH THAN 30 SEC. HAVE YOU CLEANED AND RELUBED THE MAINSPRING? EDDIE

Hi Eddie, yes, the mainspring was in good shape and I removed, cleaned, and re-lubed it with Novostar barrel grease. I also disassembled the entire clock and cleaned and re-lubed with Moebius 8030 clock oil. I used an escapement oil on the escapement, after fixing the hsirpsring of course. Thanks!

HELLO RICHARD, IT WOULD STAND TO REASON THAT IF YOUR CLOCK BEHAVES IN THAT WAY DURING EACH WINDING CYCLE THAT THE MAIN SPRING MAY HAVE A SPOT IN IT THAT ISN'T CORRECT. EDDIE

Thanks, Eddie! That will be an easy thing to check, I'll remove the mainstpring and re-inspect it for any unusual spots or damage.