180mm @ 4x5 is what @ 5x7?

so here is a picture of the finder...
anyone know this one? can i use it for my 180mm 4x5?

i think it's a finder for the Super Rollex 56 x 72.......which is a 6x7cm camera. so one has to multiply with the factor 1.7 or rather devide 180mm by 1.7 to get the corresponding lens on a 6x7cm camera.....

any concerns?

Half of the finder is missing -- you can't do much with what you have left, since you don't know what f.l. corresponds to the view you see. Look for s 5x7/4x5 Linhof Universal Sucher on eBay, and be patient. This one will have a scale of 4x5 f.l.'s on one side, and 5x7 f.l.'s on the other.