Move the rear wheel all the way forward to set the bike on "it's lines" to check the head tube angle.
I had one, I think you will find it is 72°.

Too bad the chrome is long gone. But the chrome of the period was not terrific anyway.
This is one where you might have to strip it down to assess the approx tubing type.

It is hard to tell from the rough paint, but the upper models received more file work in my opinion.
These suggest a bit on the less filed level.