How to tell if Whiting & Davis mesh bag is sterling

[cassandra2953]

I have a Whiting & Davis mess bag that belonged to my Great Aunt, 1930's or 40's.   Is there a way to tell if it's sterling at home or where would I take it to find out?   There is a small triangle near the hinge but nothing else that indicates sterling.  Thanks!

[sonomabarn67]

From what I know, you don't find rust on sterling as shown in the one photo.