A friend of mine at work mentioned that he had a "butterfly knife" given to him by his father, which he would like to find out more about. Thinking it would be one of those oriental martial-arts things now classed as 'controlled weapons' in most states, I reluctantly agreed to take a look at it. Imagine my astonishment when he brought this in the next day:

The item is a folder with an unusual method of opening. It has a thumb-slot in the back to prise the two sides apart,

thus releasing a detent, allowing it to open up like a butterfly:

The knife-handle then snaps back together in the fully open position, held by the detent. The item is heavily constructed, and of a high standard of craftsmanship.

Here is a close-up of the makers name and motif on the blade:

...and the patent number on the reverse side:

The pouch was made by Alfonso's Holster and Gunshop, Hollywood, California.

My mate would like to know a little more about the knife and the maker if possible. Has anyone seen this type of folder before? Are they common in the US? If the item is likely to be of some value as a collector's piece, he would like to know that too.

Can anyone help?