I do know that a number of 35mm/2.8 lenses were modified for close focussing, rather than macro for use by UK Government departments in the mid 70's, this was before Olympus dropped the name Zuiko from the lens front. I think principally they were used by the Customs, but for what purpose I have absolutely no idea.

I only know about them when a dealer specialising in used photo equipment bought a 'job lot' at an auction. You may have got hold of one of these.