iPhone sim card

Also make sure you give your AppleID the additional number for two factor authentication etc before switching and delete the old if you are switching permanently.

Some of your other accounts (banks) may text you for authentication.

These days your cell number is often your ID

If this is an old and disused SIM which has not been used recently, I would be surprised if it is still activated. You have to pay the monthly fee to the network, or they will shut it off - and I can’t see many paying just to keep an unused SIM activated.. It will also be deactivated if your new phone took the same number.

Could be a pay as you go sim with $50 on it. Maybe wants the old number. PAYG SIMs with my provider never die.

The OP wants to try it but is worried it might damage the phone. That’s the question I tried to answer.

It only needs to be the same physical size.

if the carrier company is different you will have to reset network settings and your wifi router passwords will be deleted

You may also need to de-register and re-register imessages.

There will be more...

Why are you moving the SIM card? It has no data on it.

~Lyssa

I agree with Lyssa. What purpose would there be in putting a SIM from an old phone you just found into a newer phone? What are you expecting to do/find?