Anyone Know What This Large "O" Cancel Is?

Hi.

I just bought an old album, probably a kids' collection, and noticed these among some common US stamps. Does anyone know what it's for? I don't think I've seen these before.

They are called "Mute" cancels

Thanks. I had a look for "mute cancel" and Wiki says it's something used in wartime to conceal location info which might fall into enemy hands. Also known as dumb cancels.

The stamp here is not a wartime stamp, however, and the cancel is unlike others I have found, which are typically made up from several concentric circles. Couln't find one like this on Google or ebay.

These double ovals are used on a variety of non first class mail not requiring a dated cancel. Most often seen on parcel post, registered mail, and 3rd class. Most post offices have one. They also come with the city/state name in them.

As you have found, Wikipedia is a very poor source for postal information. These have nothing directly to do with wartime postal location concealments.

Part of a bulk mailing:


Registry use:


With the town/state included:

Are these also called Parcel Post Oval (PPO) cancels? The one the OP shows being "mute" as in no letters or numbers.