Blue haze on coins. What is it?
Lately I've been curious about something I keep seeing on my coins and others. Can someone tell me what the light blue powdery toning or "haze" is that I have pictured below on 3 coins? For what it is worth both of the walkers shown here have some light toning on them. The mercury dime is pretty much satiny and white with the exception of the haze. I dont suspect this to be PVC even though its more easily spotted by tilting the coin or using a light source shined across the coin.
1944 walker in a rattler MS65.
1937 mercury rattler MS65FB CAC.
1935 s walker AU55 CAC Newer holder on this one.
Thanks for any help!