At 616 KB, 1B31.pdf is the largest of the 1B-coded files and is listed as a schematic, yet its name says nothing about device, maker or board revision.

A 233 KB PDF named 1B22, catalogued as a schematic, whose short code gives no device, board number or brand.

A 305 KB PDF with the short code 1B41, indexed as a schematic; the name gives no model or board, and it may be a component datasheet in a numbered series alongside 1B51…

Indexed as a schematic, this 551 KB PDF titled 1B32 has an uninformative name with no model, brand or board number.