Good point, Karel. I really should not make quick replies when I ought to be in bed sleeping!
In this case, it could be that size matters. If it is 2.5 inch diameter, then my thoughts below may be in the right direction. If it's "small" (2 inch diameter), or "miniature", then perhaps it's a nice example of a previously unrecorded design??
I think it might be a PP5 (from 1969 to 1971) because of the amber, star-cut base. But yes, the simple "1-1" pattern does not fit into the weights illustrated in books. However, the Mahoney / McClanahan book clearly shows that the PP5 was one of Perthshire's "variation on a theme" weights.