220/120 motor question, can't tell which one to use!

I got a air compressor at an estate sale that has a 3/4 hp motor. The tag on the motor is pretty much worn off, but it indicates it's a 115/230V. I can't tell which wires are the lead for the 115. Is there a way to determine which leads to use for 120? I've googled model number and frame number of the GE motor but I couldn't find anything.
Any help would be appreciated!
Thanks