not a book-binder, so cannot be sure, but was looking at a couple of 'fine bindings' and they have ridges (apparently called bands) on the spine with a line next to them - either highlighted with a gold or black line - this set would cover this for volumes of various numbers of pages ie widths - the bookbinder would apparently have a little heater with a ring of various brass head tooling ready to go before starting his/her tooling/gilding
just seen - confirm called pallets, line pallets or line tools
yours are obviously unused - with use would be darkened with heat and pick up gilt on the edge