My first thought was that they were bone trays, but they’re not curved.
Have you determined the artist “J.H.”?
“K.M.” Karl Muller of UPW is very desirable. ;-D
Not sure what the J.H. stands for but I think they are ownership initials.There is an impressed mark that looks something like a u with the tail of a y.KM was definatly there in 1876.