I am looking at a couple different eras, and see total style consistency with Helvetica Bold, and some that appear to simply be Helvetica. Characters and default kerning appear to be a match for Helvetica. I have only examined a couple different era labels on U87s.
Keep in mind that in order to obtain the final line weight, character size, etc, that it is not necessarily uncommon to commission someone to make a customized version of a font.