Are There 576 Gutter Pairs/Blocks?

I am asking this basic question because I picked up a a block of 4 with a vertical gutter that was being sold as a 576. I bit because it was one of those late night ebay auctions and I got it for very less than $3. I suspected it was really a 631 gutter block, and although I have not measured it yet, all other evidence says it is 631.

But this got me thinking, why do I not see any gutter pairs/blocks for 576, like I do for 631? I've done looking and reading, but nothing pops up. Curious as to people's thoughts.

Thanks,

Ken

Printed in plates of 400 subjects in four panes of 100 each.
Don

Thanks, Don.

I am currently reading a USSS article from 1954 (Issue 291 of The Specialist) detailing out the story of the mistake being made sending the imperf rotary press printing to Schermack's to make coils and their being rejected for the wide gutters (no lines). The flat plate version, 576, was as the diagram you showed with 2 1/2mm spacing throughout with lines separating the panes. Explains the reason for the differences... and an interesting history for context.

Thanks for the fast response. I should probably go back to pretending I'm working....

Ken