It's surely a near top end model, no mudguard eyes etc like the 1500 & 2000 models. It looks like a late '70's as you say 2500 model? The bulgier catalogue below shows the '76 models still had chrome top tube cable clamps where yours are the braze on. Second from top of the range under the 3000 of the time?
I'm no benotto expert but it's definately a high end model. Tubing would be the giveaway but i'd say it'll be SL.
'92 Merlin Mountain titanium
'93 Marin team titanium
'93 Marin team issue