grade 5 bolts not marked if galvanized?
Highly unlikely that a Grade 5 bolt (90.000 psi yield, depending on size) would be galvanized. If electro-galvanizing were used there is a high risk of hydrogen cracking at that hardness level. If it were hot dip galvanized, the required temperature of about 800 F would temper the steel to a lower strength. This tempering affect can be fixed using alloy like chrome/moly, but now you have a pretty expensive bolt; not one available in a hardware store.