If they are about 3/4" thick, you have printing blocks. These were used as mast heads on print jobs. Lead type and printing blocks were used up until the 1960's when offset printing appeared. This would have been place in a form and whatever other printed matter would be placed in the form, the whole thing inked, then a paper applied, then pressure on the paper.

It was easier to cast these then to set them up with the linotype.

I know that is a little brief, but if you look up letter press printing, you should get some good hits.

http://www.worlddaggers.com/