Bentley,

I have a feeling that the Pentax adapter cannot be removed by a spanner as you described; even those third-party ones have to use some appropriate object to poke into the slot so as to push the spring back; if a spanner was indeed supplied, it would need three hands to remove it.

There might be a chance that you were thinking of Minolta adapters for M42 (and other) lenses; the Minolta mount locks the lens in a different way and the spanner makes it much easier for installation and removal.