Vintage signed sterling silver watch band plates by 

Roy Vandever, Navajo. Very nice design that is unisex in styling. They measures 1 1/8" by 1 1/4". The pin tube measures 17mm long. The band slots measure 18mm. Together they weigh 26.6 grams. Some tarnish with a warm patina. 

Will work with Apple Watch. Mine is the 38mm. I don't know if the pin tubes will work on the 40mm as I don't have one. 

You can get the expansion part of the watch band on Amazon for around $25.00.