Hi, Does anyone know the size of the Lamson used in the original Halloween? I’m still a newbie here but I’m learning. 
Thanks,
Michael.
From everything I have read (to include dimensions of replicas), I believe the knife had a 12" blade (17+ overall length), but I could be wrong.
I believe that is correct also. It was some sort of a specialty butcher knife by Lamson that is why it is curved both sides unlike most butcher knives. If you can find a real one… Pay before you think or you will talk yourself out of it! Lol ::: Not Cheap at all from ones I’ve seen.
Keep checking ebay. I’ve seen them pop up relatively cheap.
12 inch blade, 5 inch handle. But go with the size your most comfortable with LOL. 
Overall
it should be around 17"-17.5"
Definitely the right dimensions but pay close attention to the width of the blade and the placement of the rivets when you decide to purchase that Lamson. The screen accurate knife could be a Lamson or a Dexter. Now that’s a debate that’s been going on for a while. Overall, just as I said above, pay close attention to the size details (width of the blade) and the rivet placement. I have a Lamson with the right dimensions but once I tried my best to screen match it to the hero, the rivets were off by a fraction. If that doesn’t bother you, then go for it but definitely if you’re a screen accurate nut like most of us are on here, then take another look at the Dexter, they’re made the same way as the Lamson and I have seen where the rivets were dead on to the hero. Hope this helps brother and welcome to the family! 