As Dez mentioned, it is not required, but it sure makes things a lot easier in discussions with the local authorities. I don't usually send in a photo of the gun, just its make, model and serial number, along with its caliber. They have a whack of info in their records for most of the common antique pistols. For something oddball or rare, however, a photo or two is probably a good idea.
I just email the folks with the information and several weeks later an antique letter comes in the mail. If you are in a rush because of importation, they can scan in the letter and email it to you. A letter also helps if you want to sell one to someone who is new to antiques and wants to make sure it is an antique.
However, when all is said and done, if you can show that the pistol falls into the antique classification, you don't need any letter.
