Hi Brad,
The serial no. breaks down as follows:
1442 - Engine no. in the year of production
SR1 - Type & no of cyls (i.e. an SR type, 1 cyl)
A - Normal rotation (Z would be reverse rotation)
21 - Year of production (add 1950 to get the actual year, i.e. 1971).
I believe a normal-rotation SR1 should be cranked clockwise to start it (and it runs clockwise looking at the flywheel).