During ww2 when they were issued the prime value would lie in the ability of the knife being able to perform its intended function...collector value wasn't even on the horizon and in the years soon after ww2 there wasnt much interest either...it was only 40 years ago ! i paid the princely sum of £1.25p for a pristine first issue and i can fully recommend mr Flooks opus on the fairbairn sykes if you want to see pictures of modified fs knives