Help Identify This Thing?

I have a feeling that this isn't a stamp, but I don't know where else to ask about it.

I found it in my collection. It kind of looks to me like someone used it to add up postage rates. Looks like it says reg on it for registered mail maybe?

Anyone have any insight into what this is? And why would anyone hold onto it in their collection, if it is just someone doing math on a scrap of paper like I think it is?

Thanks in advance.

[2c]

Left side, first.

1st line: "5g", eg, the weight is 5 grams.

2nd line: that blocky "T" is for postage due, mimicking the ?more common rubber stamp.
.
I'm guessing "Avion" signifies "what would be the airmail rate".

3rd line: The actor E.G.Marshall would say that his initials stood for "Everybody Guess".

4th line: the "10" in the box is the postage due.

Right side: the math.

[/2c]

Cheers,

/s/ ikeyPikey

https://goscf.com/t/39143 ... edited to add a pointer to a useful thread ...

... and to, uh, answer your question: it looks like a piece of selvage from a sheet of stamps was used as Your GrandFather's Post-It Note.

Wondering if avior is abbreviating avoirdupois, and old weight and measure system. Haven't heard the word since pharmacy school in about 1977, and certainly don't use it either!

Hope this is helpful....Ray