I’ve been following this seller on eBay for a long time. I’ve even purchased helmets from the seller. He make great custom pocket helmets. His ebay handle is TravisTomMark.
The white helmets were made by TravisTomMark. They show alternate logos and facemasks. I particularly like the Lions and old Ravens logo with the gold facemask. Well done!
For clarification, some prototypes are a design a team seriously considered using, but never did. Other prototypes are fun helmets collectors make on their own. Underneath the white prototypes are some photos of prototypes I have made and are in my collection.
Riddell NFL Pocket Pro Helmets 