I'm organising to view this, but it's some distance away. The seller has had it 13 years and bought it new. She don't know if it has any markings, she doesn't want to go lifting or moving as her son took the pictures and he's away at the moment. Does anyone have any other ideas, other than the markings on the underside of the frame? There is only one screw/bolt at the top of each leg, which is contrary to the 3 on the LC4 on Cassina's site. However, I have seen older ones that claim to be original with the one. The seller also sent me pictures of the brochure. I couldn't get any more out of her, not techie and she just wants me to see for myself(it's hours and hours and hours away!) I've emailed Cassina but have yet to hear back. Any insight would be appreciated. 
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If it is by Cassina and it is from the last 13 years as claimed, it should have the I Maestri stamp on both parts. This is also accessible through Cassina's website.
http://www.cassina.com/en/lc-collection/authenticity/identity-card-and-i...
Without this mark, it is an unlicensed version and this is where you need to use your own knowledge to determine if it is a bad vs. a good copy. If it is so under priced even if it is a bad copy that you just want a place holder in your collection for now, by all means...
The shape of the bracing is elliptical on the really old examples and oval in the reissues.
http://www.design-museum.de/en/collection/100-masterpieces/detailseiten/...
http://www.cassina.com/en/lc-collection/authenticity/how-to-tell-origina...
Thanks Minimoma, I'm not willing to spend the money on a replica. I'm fairly convinced that it's a replica, as I didn't recognise the brochure of the store where it was bought originally. It's too far to travel really on the possibility I can find the markings when the owner can't!
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