It's a simple voltmeter, possibly with a load included, to measure the individual cells of a battery. Some industrial batteries can have cells replaced as needed, and you use this to check the cells.
Looking at it, it seems to be just a simple volt meter. The two way needle looks as if to measure the absolute voltage if a cell, without consideration to positive/negative polarities
In short: volt meter with a guide to try and correlate cell voltage with cell condition