[Dx-qsl] best way to save postage stamps

[FireBrick]

Sorry for the off topic.
I don't REALLY collect stamps but I'm saving all the return Air Mail envelopes with
foreign stamps as maybe my grandchildren will get the bug.

I use a letter opener to slit the top of the envelope.
Is this the best way, does the envelope have any value or just the stamp.

If a envelope like this one from Iceland just has a machine stamped postage, should it be
saved also?

I've got a couple thousand old envelopes with stamps still on them.
Is this the best way to save them?


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Bill H. in Chicagoland