All six of the hydrometers appear to be in good condition but I have no way to test them for functionality or accuracy.
It looks like they were previously owned by Apex Oil Company although some of them still look brand new and unused. Five of the six boxes have a temperature range written on them with a cumulative range of 29-81 and one of the boxes has “black oil” written on it. Some of the boxes have paperwork and varying types of packing materials inside.
There is an old booklet dated 1952 previously owned by a refinery titled “Table 5 Reduction of Observed API Gravity to API Gravity at 60F”. The front cover is detached and there is handwriting on it and it is folded in half.
There is a receipt from Fisher Scientific to Apex Oil dated 1974 for a hydrometer. I would speculate that at least one if not most of these hydrometers might be from that era.
Look closely at the photos for condition and details and don’t hesitate to ask questions.