Dimpled chainstay, so not a 3000 (though the dropouts are Campag) ; top-of-the-chainstay cablestop = 1977 or 1978; what diameter is the seatpost - 27.2 = 2500, 27.0 = 2000, 26.8 or 26.9 = 1600/1500/1000/850(?), 26.4 = 800.

Where is the serial number, does the BB shell have an I stamped in it, is there a bb cutout and if so what does it look like. Mexico built mid-range Benottos have a deserved reputation for cracking in the bb shell area.