This is my first post to this excellent forum. I have large two large masonary fireplaces in my home and wish to obtain inserts for both but I'm on a tight budget. I am currently looking at an older lopi on craigslist which looks to be in good shape. The owner doesn't know the model number. I have attached two pictures. From my readings in this forum, I think it is a version of the Lopi 520 or LX possibly from the 1980's? Please help me ID this insert. Additionally, its previous installation was just slid into a masonary fireplace directly exhausting into the flue. I know this is not acceptable for current code. So, a critical question I have about this insert is whether or not I can use a stainless liner/block off with it? thanks in advance.