The limited availability of "NEW" or "NOS" Mainsprings leads me to often have to compare what I have with what I need by using my Swartschild chart to find a similar size spring. Recently, my 18s Hamilton stocks were reduced to mostly "motor barrel" behemoth springs while I still had many of Hamilton's fine double braced 16s "Motor Barrel" springs left. Investigation shows that in fact the 16s Motor Barrel is the same width and near same thickness ("strength") as the 18 size "T" end.

So far I have used two of the 16s springs to VERY SUCCESSFULLY replace and re-time 18s, 17 Jewel Hamiltons. There are many other "parallels for mainsprings, but in every case, I Measure the width and thickness of the "Old" and "New" springs before trying to use them. With the Hamilton all that is needed is to carefully file back the Brace tab width to the necessary shorter width used for the original "T" end spring.

If you want NEW Swiss Hamilton and links to all the other brand White Steel Main springs, go to

http://www.jewelerssupplies.co...lton-mainspring.html