Hi All, could someone please, please tell what # Hamilton mainspring is required for a 23j Ball 998E? Would it be the same spring required for a Hamilton 950E? or 950B? Thanks in advance. Joe

Joe,
That spring is the same as a 950E which uses the 950 spring. It is part # 534, Motor Barrel, strength 16 ½ refill No. 210. I think there are several of these in my parts drawer that are original Hamilton stock. Let me know if you need one.
RR

Hi Rich, thanks for the reply, I was able to find one also. best regards Joe