Barcodes on old comics Vs. Spidey's face?

[Belacose]

I've noticed that most issues of the Amazing Spider-Man #252 (1st black costume) that are up for auction on eBay have a barcode on the bottom left corner, however a couple of them have a black/white picture of Spiderman's face instead?... Does anyone here have any clue as to why this is? Is this possibly a difference between newsstand and personal subscription? Anyone?

[Captain Bob]

Marvel in the 80s put barcodes on newstand and retail store copies, while putting pictures (often Spidey's head) on comic shop and subscription copies. When the practice started and stopped I do not know.

[Belacose]

thanks, Captain Bob:)