Neil, yes as ODH say's I was on a bunch of f.a's with fants in the 80's and unfortunately as a result now suffer chronic PBWFSD (post Bungonia with fants stress disorder) blanking out all memory of the place. However if I dare to peak back into that terrifying time I do remember slope’n sope’n being desperate and unlikely (and with dodgy bolts?) but obviously that’s not the route you are talking about, and I do remember being responsible for hand drilling what are probably now rusted crap bolts while putting up a couple of those (crap) single pitch slabs right of pulsar (one being a single 12mm bolt, hanger and locking steel biner on top to rap off?) but the bolt line you are talking about doesn’t ring any bells at all.
We used to keep a log book in camp pritikin (the flat ground under the low roof line left of jewel box), fants had a tin garbage can buried there to stash stuff. everyone kept this log book up to date with new routes and repeats at the time, it contained a lot of epic yarns from local and visiting OS climbers (doug scott even!), sadly this disappeared. It may have held a clue to your discovery, though the bolts as you describe them sound pretty ancient.