Specimen Vs Proof Like

I have started collecting / building 1967 sets:

Proof like, Specimen, and Mint State. Lots of fun, as there are probably 30 or so different ways to makes sets with all the different grades, cameos, and then MS,PL, and SP.

I know how to tell the difference from early PL or Specimen coins up to 1949 lets say.

I know the difference in modern Proofs, and "modern" specimen.

However, I can't tell the difference in 1967 PL vs 1967 SP. ? The coins look so similar in every way.

Specimen coins up to 1949 look like Proof Like coins to me. I have several specimen coins in the 1940's I can tell the difference easily from Mint State.

After that ; I'm in trouble. I can't see any differences in a 1967 SP66 25 cents vs 1967 PL66 25 cents.

Can anybody fill me in on the "tells" of identifying SP over PL during this period? What am I missing?

I know modern day Specimen are easy to pick out;