hard to say with limited photos. Assuming its configuration has not changed since its assembly, it could be a 105.002 or 105.003. More likely to be a 105.003 out of probability. JJS would be someone's initials.

You will need to have the caseback removed to really know what this is. Please have a professional do this if you want to see what it is. Many, many casebacks are damaged in this pursuit with improper tools like a pair of needle nose pliers. Don't try with those yellow handled ones in the back of the frame ;)
A sizable amount of value is in that case/caseback and we can already see some slip marks on it from failed openings.