Quarter plate is very similar to 9x12, and 9x12 is definitely LF, modern 9x12 double dark-slides have the same outside dimensions as modern 5x4 holders, both fit International backs.

It becomes a woolly area because many pre-War 9x12 cameras (mostly German) were substantially smaller and lighter than 5x4 cameras. 5x4 is 10x12.7 cm, so only a fraction larger than 9x12, here's an example:





OK that's at the \extreme the on on the right is more typical



Ian