Hi, I just moved into a 1976 split entry home in Minnesota 6 months ago. I want to install an insert into the old origional prefab fireplace, but I can't identify what kind of fireplace it is. The writing is so faded, but I can barely make outsomething like Model: 8F-36... I can see that it is a "zero clearance fireplace." I can also see that it has the UL logo in the upper left hand corner. The only other thing that I can make out is Minnesota which is writen in small letters in the very bottom righthand corner of the metal plate. I really appreciate any help you can give me with this. I'm also trying to figure out who built the house from the city. On another note, I have already purchased a Century CW2500 insert. I'm hoping to be able to install this insert because it seems like a great value. I also don't want to burn my house down, so if it comes to it I can return this insert for something else. I talked with the manufacturer and he basically said that this unit is only tested for masonry fireplaces, but that figureing out if my old prefab unit is able to have an insert installed into it would be the most important next step. I should have done more research first, but the insert was on sale so I went for it. I do plan on installing a 6 inch s.s. liner to get the proper draft, and to help with making the chimney safer. The old prefab seems to be in decent shape. It has a 8" inner, 10" outer chimney that seems to have insulation between the two. I don't know for sure, but it doesn't sound hollow when you tap on it. The chimney only has around .5 inches of clearance to the exterior sheathing of the house right at the top of the fireplace. Another note is that the fireplace doesn't have much clearance to the exterior sheathing of the home. In some places it may even be touching on the sides. Pink fiberglass was shoved all around the unit between the wood and the exterior of the metal box (I'm assuming the heating contractor that the builder hired did this, or maybe the insulator thought it was a good plan to help stop drafts from the outdoors.) If the prefab unit was taken out and the new Century sits where it is in my picture there would be over 20 inches of clearance to combustibles on the top, 8-10 from the back corner going diagonally back and to the sides, and over 20 if you go straight back. I've talked with my local building official, and he didn't seem to know that much about the details... I'm very glad that I found this website as there seem to be very knowlegable people on here. Thanks for any input.