The ASP was a converted Smith & Wesson model 39.
The gun was slicked up in action, the hammer spur removed, I believe the barrel and slide were shortened, the sights were replaced with a very ingenious and hideously useless sight device and the clear grips to count rounds.
I used to know the name of the man and company that did the conversions and have forgotten. They only made the conversions for a few years and then the major manufacturers and liability insurance caught up and put them out of business. There are some still around and they are collector's items.
I've read all the Ian Fleming James Bond stories and several of the others. Frankly, the Ian Fleming stories are the 'authentic' ones. All the rest are close but no cigar. The John Gardner stories are pretty fair, but the protagonist is not the same Bond as Fleming wrote.
Interestingly, in the Ian Fleming series, Bond carried and used a number of handguns. The two most common mentioned are the .25 Beretta and the Walther PPk. However, Bond was also issued a Colt Detective Special and a Smith & Wesson Centennial. In one report, Bond wryly includes "Inform armourer, Smith & Wesson revolver ineffective against flamethrower."
He also regularly kept a Colt Police Positive "...with sawn barrel..." under his pillow when he slept and carried a "...long barreled Colt 45..." in his Bentley for car to car shooting. No one seems to know if that "Colt 45" is a Government Model or Single Action Army. From the long barreled description, I've always thought it was a SAA. But I can't prove it and no one seems to have asked Fleming prior to his death.
Incidently, Mr. Fleming admitted he didn't know much about guns. He did serve in the British Army and was trained and proficient with issue weapons, but that was the limit of his personal experience and knowledge. In fact, the gun in the stories listed as a "... .25 Beretta ..." was written in the rough draft as a .28 Beretta; Fleming might have meant a .38 or .380 instead of the .25 ACP version.
In the movie where Bond has his .25 recalled, he is carrying a 1934 or 1934 Beretta, which would have been either a .380 ACP or .32 ACP pistol, depending on model. Which just goes to show the movie makers knew less about guns than did Mr. Fleming. I note with some humor Fleming describes the PPk in the book as in .32 ACP caliber. Now that's a real barn-burner.
Oh. The .25 Beretta Bond carried had a suppressor, but we never are told from where it came. Bond possibly picked it from the suppressor bush across from Secret Service HQ.
