Information on Brown and Sharpe Calipers

Hello! My name is Eric. New to this site, new to fourms in general also. I have digital calipers from Brown and Sharpe (Digit-Cal Mark 2 EDP 50700 with the numbers 599-573 under that on the box) they belonged to my grandfather a tool and dye maker. I am interested in finding equivalent batteries for them so I can use them. The calipers are in great shape but haven't been used in probably a long time as the batteries that were in them say Made in West Germany. So I'm assuming these calipers are from the 1980s, probably mid 80s. They are mercury batteries P625 1.4 v. Have tried a set of 1.35 v zinc batteries supposed to be an equivalent to the mercury battery. Bought them at a camera store after doing some research on the battery itself and I found they were very popular amongst photographers. They haven't worked. They won't turn on. Wasn't sure they would as the originals were 1.4v and these are not the same volts but I gave it a shot. Any information on the calipers themselves would be great. I'm not interested in selling, I just don't know much about them. However most importantly thought I am looking for batteries that would work so I could use them. I have photos of the box, and the calipers themselves and once I figure out how to post them I will. Thank you!