The one on the left looks like a "gravestone slugplate" to me. See Maquoketa Iowa hutchinson bottle on eBay. I have mine on there and it has a gravestone slug, one of two in Iowa!
I neglected to mention the fact that these bottles are from the late 1860s and the one on the left is the reworked mould from the other. They are smooth based and well embossed on the other side "Beaver soda water works Registered Trade Mark" with a beaver. the good camera was just a lend so here's a bad pic of the other side.