Use for 16 x 20 ortho plates?

Can anyone tell me what 16 x 20 Kodak Glass ortho plates were used for in the 1970s?
http://futuresaleshome.com/img/Kodak_Plates/label.jpg

Astronomy? Graphic Arts? Stained Glass?

thanks,
Ed

Given that they are a) glass, and b) lithographic (per the developer recommendation) they were probably used for something where dimensional stability was paramount, possibly cartography, the making of masters for photomask reduction, or large-scale reticles. Why they would be ortho rather than blue-sensitive is a bit puzzling.

Very interesting---I hope someone can come up with an authoritative answer.