Triumphs had two different types of hard tops during the TR run. The rarest is the Surrey Top, which was the world's first targa top, offering a hard, quickly removable center section, as well as a bolted-on rear section. Surrey tops could be found on TR4, TR250 and I've heard of a few on early TR6s.
More common is the standard removable hard top, which made its debut on the TR2. Usually affixed by three (for works rally cars) or four bolts in back and three on the header rail, it's a two person operation to put the thing on, and a one person with long arms task to remove.
By the time TR6s came around, all cars came with standard soft tops. If the car you're looking at has only a hard top, it means a previous owner removed the top frame and convertible top. You should be able to replace a missing top via parts from Moss Motors, Victoria British, The Roadster Factory or ebay.
It's not necessarily hard to install the hardware, although if the snaps are missing, you'll need to reattach snaps to the bodywork for the soft top. The TR250/TR6/TR7/TR8 top design is fairly simple to work with (not as easy as the four-bolt TR3 frame and completely removable fabric, but still easy in comparison to, say-- a Chrysler Lebaron.)
Check out a Moss Motors catalog for all the parts and diagram for how it all fits together.
[ 04-04-2004: Message edited by: sammyb ]</p>