Oftentimes, people pretending to be ex-military will make some sort of claim to have been in the special forces. There is a way anyone can verify if the person is telling the truth; however it can be perceived as a challenge to that person's honor. It is a little known fact that authentic members of special forces units (whatever branch of the military) commission, at their own cost, special coins carrying the logo of their unit. Authentic members carry this coin with them at all times. There is a tradition called the "coin check" whereby you can demand that the person claiming special forces status produce the coin. If they are legit, they will dig it out of their pocket and slap it down in front of you, after which you are obliged to buy them a drink. If they fail to produce the coin, they are phonies and should be shamed out of the house. Hope this helps.
My only brush with military service was getting drunk and getting stommped by a Marine when I was a teenager. I think I experienced a few special forces that night too.
The coin check is a pretty weak authentication. For one, you are supposed to have also served in the unit. It isn't like anyone and everyone can go around asking for a coin check. Secondarily, I know a lot of people who don't carry their coins around with them. Them not having it is far from conclusive. For that matter, so is them having it...many units hand out coins as a form of thank you to other people. I've seen entire collections for sale.
Not all units have challenge coins commissioned and the ones that do exist can be bought on Ebay or through mail order houses by anybody with the money.
Oh, bull. Pure, unadulterated, malarky.