This is Rock Lobster MTB frame # 0128. I think it is from 1991. It started its life as a fully rigid bike and has been in use for most of the last 27 years. Now it will have a new front end paired with a Fox fork and a disc brake on the rear. Bike collectors might be angry to see an older bike get re-purposed like this but the owner wants to keep riding it and these changes will make the bike much more useful to him.
While the bike will have a modern fork and brake set, the frame will retain the old look with bronze fillet brazed joints. The tubes are larger diameter but from a distance the frame will still look like it did before the work was done. This is an old customer and this kind of re-do is something I normally do not take on. You might be looking at the last one right here.