1956 Buick Special speedometer repair

[hudini]

Hi to all
I need someone to tell me on my speedometer, should the indicator for mph, when i turn it with hand go easy or "not easy".
The best would bee if someone know on what rpm should mph show. for example, on 100 rpm - 10 mph.
on pics you see, when I turn it with hand it does not go back to 0 mph. sometimes it goes.
thanks

[JohnD1956]

Have you loosened the nuts holding the back cover on? Just unsnug them a bit and see if it helps.