Can I use my iPhone 15 model # MTLV3LL/A on a European network with a European sim chip?

If its not locked to a specific carrier, then yes.

Check Settings ➜ General ➜ About ➜ Carrier Lock.

If it says "No restrictions", it can be used with any carrier.

Do note, that is an American model and as such does not have a sim card slot, so can only be used with digital SIM cards also known as eSims.

In Belgium carriers that support eSims are:

Orange

Proximus

Telenet

Ubigi

click here ➜ Find wireless carriers and worldwide service providers that offer eSIM service on iPhone - Apple Support

Also, make sure you prepare it to give it to your grand son by following the steps in the link below.

click here ➜ What to do before you sell, give away, or trade in your Apple Watch, or buy one from someone else - Apple Support

Did you purchase the iPhone 15 in the U.S.?

We ask because the iPhone 15 version sold in the U.S. was eSIM only. There is no traditional SIM capability with this version of the phone, although the phone can probably be used with a carrier in Belgium if they support eSIM.

Tap directly on MTLV3LL/A and a 5 character phrase will appear. It will start with an "A". Example.....A2846.

Please post back with that 5 character phrase, so we will know more about the capabilities of your iPhone.

Servant of Cats wrote:

Re: “Also, make sure you prepare it to give it to your grand son by following the steps in the link below.”

I think you meant to post the link for iPhones, not the one for Apple Watches.

What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support

Tis true. Pasted the wrong link. Thanks.

Re: “Also, make sure you prepare it to give it to your grand son by following the steps in the link below.”

I think you meant to post the link for iPhones, not the one for Apple Watches.

What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support