Vintage box art sketches question - seeking advice

[Webstor1983]

Hi,

Recently saw a sketch of Zoar on ebay that the seller claims was done by a Mattel artist for the back of boxes. Took a chance and picked it up, but am not sure what I have, if anything.
The original ebay listing (not sure if I can include the link) included 2 conversations that seem to verify authenticity as "crosscel or cross sell", but I'd like to know more as I'm not convinced. The sketch is on a transparency of some sort. It looks to me like a trace of the photocopy (on very old/worn paper) of some internal Mattel notes on box art, but why would this have been done? Wouldn't original sketches have always been on regular paper, etc? Any info about how the box art processes for the vintage line would be really appreciated.
Thanks!

[TOKYONEVER]

Can you post a pic please? it will be easier to help you with a visual.

[mexicantoys]

I saw that auction , in fact he posted twice, hard to say it was original (so easy to make a fake drawing of that piece) so I guess the story behind that piece is the key.

[TOKYONEVER]

I just found the sale, I am adding the pictures here.

[Lich Leech]

That's some beautiful line art!

[Lich Leech]

So what do you guys think? Does this mean that Errol McCarthy did all the cross sell art as well as the artwork at the tops of the card backs? The He-Man drawing is definitely by Errol, and from context it appears that he did Zoar as well.

[Webstor1983]

I'm really curious, myself. I'm still not sure what it is that I have. Thanks to all who have looked into this so far. If you have any other insights, please share them.

[Jukka]

So what do you guys think? Does this mean that Errol McCarthy did all the cross sell art as well as the artwork at the tops of the card backs?

William George has been mentioned to do cross-sell watercolor arts. Not sure if he did all.
Erroll McCarthy seems to have done majority of cardback arts.
Dave Stevens did couple (Spikor, Moss Man)
Some artworks like Horde Trooper don't look like Erroll's work, but no info how many artists helped illustrate the cardbacks.

Bruce Timm and William George worked on the later wave frontcard artworks.