I took a look at some of the freewheels I have on hand, some mounted, some still in the box, with variations:
4-speed Regina G.S. Corse S.I.C.C. ERATE, engraved, gray body, notch removal, no date code. Not sure of the date for this one, 50's perhaps?
5-speed Regina Extra Oro, gold cogs w/gold body, engraved, made in Italy, notch removal, no date code. I'm sure these came from the early 70's.
5-speed Regina Oro, gold cogs w/gray body, laser etched, made in Italy 80, spline removal.
6-speed Regina Corsa, gray cogs w/gray body, engraved, Italy 78, notch removal.
6-speed Regina Oro, gold cogs w/gray body, laser etched, Italy 81, notch removal.
6-speed Regina Oro, gold cogs w/gray body, engraved, Italy 83, notch removal.
6-speed Regina CX, silver cogs w/gray body, engraved, Italy 85, spline removal.
It appears you could find freewheels with spline and notch removal in the early 80's. Also in the 80's you could find both laser etched and engraved freewheels.
Richard Robinson
Jacksonville NC