This topic has been worked over before, and reluctantly I must agree that on some denominations (esp the penny!) the "VIP" status seems to be reflected in minor die differences. But the logic has in general IMHO not always been pristine and the RM also IMHO has not always used the same prep for proof or specimen sets and there are borderline coins that received some but not all the attention one usually expects on a proof of any description.
A couple of years ago, I bought from Heritage 1953 1/4, 1/2 and 1 Penny coins that were all in Proof 67 Red Ultra Cameo. They were and are beautiful and although not matching the VIP coin die characteristics seem to have received some special treatment.Also I have an ex-Norweb Proof 64 1953 penny not of the VIP type but was sold to them as a "special striking". Other examples I could point out, certainly.
A crown such as above in a "proof deep cameo or ultra cameo in 66 or 67" would be very hard to differentiate from a VIP at times and frankly the price paid for the above crown or half crown simply ridiculous.
As a footnote, many of Bull's listings of "VIP proofs" from the 1940s are questionable as proofs from the off years would be VIPs with some perhaps having more cameo effect than others.