Which component is this?
Probably a DC-DC converter. 9V isolated output most likely, not sure about the input voltage. See this ephemeral eBay listing for similar products.  

If the first character in the part number is a 5, then maybe 5V in, and the 075 could indicate 7.5V out, but 9V was more common. Try hooking 5V to it, with some reasonable load on the output such as 1K and see what voltage you measure.