Purple Shaft cam IDing

Direct Connection # was P3412016 - for a small block......Cam # was ST21-108

Duration - 28x?? my data sheet has a bad spot on the third digit, sorry
Lift - 0.520" (at the valve)
Centerline - 110*
Lash intake - .018"
Lash exhaust - .022"
Recommended spring - P3412068

This one appears to be the closest to matching your 0.523" lift spec you stated. Easy to have 0.003" discrepancy due to measurement error and/or manufacturing tolerances.

Hope this helps you ID it.