If your vehicle has factory "tint", it's actually the glass itself. It's called privacy glass. The easiest way to tell if it's factory or not is to look on the edges - it'll be obvious.
As far as windshields, check with autoglass shops if there's an OEM or aftermarket replacement option that has a solar coating or lamination. If you have a chip or broken windshield, and insurance is paying, you might be able to get the glass shop to order you a new windshield with the solar protection - you might have to pay extra for it, though.
If you all are interested, there's a small line on the front windshield, where the shade ends. That marks the limit aftermarket tint can be legally applied. It's usually on the passenger side.
3M is the best tinting film. But then again I've been out of the business for years and things my have changed.
As far as window tinting laws in NM, there are some, but nobody cares. I've seen 15% on front windows.
Years ago I got a ticket for tint on the front windows on one of my cars - the cop was looking for anything to ticket me on. I went to the APD parking lot and took pictures of ALL the cars in the lot with dark windo tint. Almost all the private cars had limo tint and some of the PD vehicles had limo tint on the front windows, too.
I took the ticket to court and you know what happened - dismissed.
I've seen it on windshields and unless you're right up on it one can barely tell.
