It's hard to alter a serial number and not leave any traces.
Colt stamped the serial numbers of revolvers on the frame, on the cylinder crane, and inside the side plate.
Removal and change to a different number will leave traces.
The Colt Boa had special Boa serial numbers, a Python type barrel, and a brilliant Colt Royal Blue mirror finish, all of which yours have.
I haven't seen a fake Boa, but I've heard of Colt Trooper Mark V's someone fitted with a Python barrel, which is what the Boa basically was.
These are not easily mistaken for a genuine Boa because of the non-Royal Blue finish and the Trooper Mark V serial numbers.
Usually faked Colt's involve changed barrels to rare lengths like the original 3 inch barrel Pythons, non-factory engraving, or fake Custom Shop models.
Certainly a high value model like a Boa would be something a faker might attempt, but it's not likely it would pass the smell test of anyone even moderately familiar with Colt's.
I'd say that the chances that these are not genuine Boa's is very slim.
You can order a Colt Archive letter on them to confirm that they are Boa's and as long as the serial numbers haven't been faked that's pretty much proof positive.
The market prices for Boa's is nose bleeding high due to the rarity and them being a Colt "snake gun".
As for having them looked at by an expert, that's probably not going to be of much use.
Unless there are signs of a refinish to Royal Blue, signs of a barrel change, or removed and re-stamped serial numbers are obvious an expert will usually have go on the serial number.
