[Mark70Z]

Ben,

Really like the look of your Maris blank back card. Like some have said I wouldn’t have an issue with trimming to normal size since it looks to be hand cut already. I have a few BB cards and they are all regular sized.

I’m not a slabbed card fan so I wouldn’t encase it, but it wouldn’t be a problem if you choose to do so if you like the look or want to sell that way. It may get a few extra bucks listed as authentic and blank backed.

I don’t know if there’s a way to tell if a blank back is an error that was unintentionally put in a pack, a blank backed sheet that was cut or from a discarded scrap. In your example it’s likely it was from a scrap sheet that was cut.