Quite interesting - the Stroud 6-1/3 does look to be the same gun shown by Buck25: check the ding in left side of front sight, position of pivot and lock-screw slots, apparent repaint on left grip emblem. Someone got a bargain in Sweden, now cashing in!

To me the caliber stamp looks real, though typical marking is:
Kal. 4 1/2 mm
cal. .177
So why would they get lazy on the odd gun(s) - possibly a factory worker's personal dart-shooter?

Don R.