shard ID

[toddrandolph]

I found this shard in my garden this morning. There is a CB monogram and it looks like there is a shield around the monogram. Heavy amber glass, looks like it was a bottle base but there's not enough left to tell. My house was built in 1870. I don't find a lot of real old glass pieces here, but nearly every hole you dig yields at least one salt glazed crock piece. Lots of 1858 mason pieces as well. Oldest piece I have found here is a tiny shard of a scroll flask. Any ideas?

 

[carobran]

that design looks familiar but im not sure where ive seen it[8|]

 

[toddrandolph]

Just realized there is also an I in monogram