Is This A Stamp Or A Sticker?

I did a quick search and it looks like maybe it's a post office in Italy. I'm wondering if the post office put it there or the original recipient placed it there.

The first post shows a registration label affixed at the nr. 9 branch office in Venice, Italy.

I am not sure if Italy had a scheme under which a large user (company) could affix the registration label and hand the letter and registration ledger into that branch office. But the label is from the post office and shows the number under which the item of mail was registered through that branch.

The label reading 'PAR AVION' is a label that tells the post office the mail should be carried by airmail. You could get these at the post office. They could be affixed at the post office, but also buy stamps, ask for the labels and affix them at home.

The yellow label also is a label and not a stamp.

This thread describes these A.O "Autres Objets" labels:

https://goscf.com/t/78242

The blue airmail label is called a Postal Etiquette
More examples here https://goscf.com/t/12126
Don

Awesome. I've not been to other stamp/ collectibles forum but I can't imagine any of them having the same quality of members as this one. Not blowing smoke. Even when I get corrected I feel it's genuine, like it's a teaching moment for them. I bought a bunch of stamps for $100 a few years ago and didn't think anything about it until the other day.

I may be transitioning into a collector instead of one who was just going to sell what I have and be done with it. This has been a worthwhile experience.