what does it mean on tintype plates?

[jim young]

I see this on antique tin type civil war photos, 1/6 plate. 1/4 plate, does this refer to size?

 

[Old Soldier]

Yes. Full plate is 6½" x 8½". The fractions will vary on the fractional plates for some reason. Try:

Early Photographic Processes - Sizes of Photographs and Plates and Negatives

Since these are direct prints, they do not always accept enlargement from photos of them and the coatings are often subject to atmospheric deterioration. They were cheaper than the altenative - coated glass negative and print - but this method tends to survive longer and retain much more detail due to small grain size although they can crack and suffer fom edge deterioration. You can't win them all!

For the full list see:

Plate sizes - Camera-wiki.org - The free camera encyclopedia

camera-wiki.org