Such crosses were worn by the choir members (and still are) over their cassocks & surplices. We are, of course, quite taken by them as they are vintage.
This style of cross would be excellent for assemblage jewelry as the surface on either side is absolutely flat - so that you can add your embellishments easily with adhesive or solder. Or, you might choose to change the ribbon that holds them and add a chain or leather thong for a different look.
We have not cleaned them in any fashion - that's up to you, should you choose to do so! Many of them are patinaed and look even better (we think) than they might have as new.
The cross measures 2-1/2 inches tall (including the hanging loop) and about 1-1/2 inch from side to side. Each cross arrives with a rattail cord or ribbon (most are black; some have faded) and with a case so that the choir member might carry it along to the performance safely.