I'm wanting to revive a vintage Taylor-Hobson Talyvel inclinometer:This specimen calls for what appears to be a pair of absent "Mallory battery SKB-830" units for power, which comes up unknown on a Web search. From the enclosure and connections it looks like these might have each been a cylinder about the size of two C cells in series with snap tabs similar to a 9-volt battery but larger. The battery test meter appears to be testing for about 6 volts. Maybe 5.4 volts if it was four mercury cells at 1.35 volts each.
Any ideas on what this battery might have been? All I can determine is that the Mallory SKB batteries were the mercury type developed during WWII