European tongs hallmarked 878M: silverplate?

[salvo]

I have this pair of tongs with a hallmark I cannot find anywhere: 878M. No other marks found. I suspect they are plated but not certain.

[Traintime]

Reference--Assuming that this is not a maker's mark, the only prior reference to an "878" (called "stamped" in that case) was related to part of a tea set in this older thread for which the photos appear lost: viewtopic.php?f=26&t=17471&p=39292&hilit=878+mark#p39292