Many claim that the knife used in the original Halloween was a Lamson brand kitchen knife. While that may particularly be correct, this prop knife from the film proves otherwise. As far as I know, that isn't a Lamson. Different design.
The guy who posted the pic also has a bunch, I mean a BUNCH of other behind the scene stills. I think it's worth checking out; many were new to me. The link is: http://www.flickr.com/search/?q=halloween+myers
They start getting really good around page 14 or so...it's just a really cool thing to do if your bored and online. Some really neat pictures, don't take my word see for yourself!
(I know it's a search engine, I was just as surprised as to the amount of content I haven't seen before).