Cat,
Hmmm. My late 80's vintage 105 6-speed freewheel takes the standard Park FR-1 splined freewheel remover. One would think that all the 6-speeds would use the same tool. Some older Shimano freewheels may have a plastic dustcap that must be removed to expose the two lugs/notches for the removal tool which would be a Shimano TL-FW10. But I would have thought those would all be 5-speed.

Maybe one of the gurus can solve the puzzle.
Regards,
Raymond