Hmmm something doesn’t look right to me. The pressure or force used to create the signatures appears to be quite excessive leaving strong indentations in the cover. This is not seen on most of the signed covers I have seen.
If you take a closer look at the signatures you can see lots of hesitation in the strokes. This set lacks the free flow of a genuinely signed item. I’d say this one is a forged item.
I’d hazard a guess and say that these signatures were traced onto the lp cover making deep grooves that were later gone over with a ball point pen to give the illusion they were hand signed genuine signatures.