Yeah, that's what I'm thinking now as well. When I first dug it I had thoughts of Trade Silver in my head. It came from a site where Trade Silver would not be unexpected and its one of the last targets on my bucket list...
Whites Spectrum XLT, Garrett AT Pro, Macro pinpointer, Garrett carrot pinpointer,
Lesch digger, Nel Tornado coil for ATPro, Garret ATMax with Nel Tornado coil
Yep typically with pocket watches and serial number locations you would have the same serial number (in one form or another) on each piece of the watch like body of the case, inside workings plate and bezel ring. Because it was often difficult to stamp the bezel directly, many times the last few digits of the serial number that was marked in regular (arabic) numbers elsewhere would have roman numerals on the bezel. In your case if we could see the other serial numbers I bet the last three digits of the number would have been 4 2 6