I ran into another one of them today. The guy wanted $400 for it. I ask him if he was aware it was a Chinese knock off and he said he thought it was. No doubt in my mind, serial number was 8888SC, and stick on Leupold badges made of paper. He said its still was a good scope and well worth the $400 he was asking for it. I chuckled and said last one I had the adjustment knobs fell off and there's no warranty. But they are still good scopes for the money. I just said I was glad it was his and not mine and walked off. I'm sure after I left it will go back to being a great scope for the money.

If I’m buying a used one, I always call Leupold and verify the s/n through them.

I've seen the 8888SC on several bogus Leupolds. Seems that's the serial number they use on all of them. The guy claimed they sold for $700 on Amazon. That's hard for me to believe but I do know you can get a Leupold for $400 that is real with a warranty. Not a top end but a decent scope. Why buy a POS fake that there is no doubt sooner or later (and probably sooner) its will take a crap.

Are these usually a certain model or do many models have knockoffs?

The ones I've seen most of were the Mark IV.

This is definitely a knockoff. It came with a Ruger 10/22 I bought and it has been fine.