The M77 Flat Bolt in the short action ie., 22-250, 22 Swift, 250 Savage, 243, 308, 6mm, 284, 6.5 Rem.Mag and 350 Rem. Mag was made from 1968 - 1974. Serial numbers start at 1 up to the first few thousand of the 71- prefix. The Long action Flat Bolt, 7x57, 25-06, 270, 30-06, 7mm Rem. Mag., 300 Win Mag, 338 Win Mag was very short lived - introduced in 1971, the Flat Bolt was soon replaced by the Hollow Bolt and then by the Round Bolt all within a few months of production and all mixed in the serial number range with the short action Flat Bolts. Probably only 3-4 thousand produced. The "advantage" of the Flat Bolt is the Style and the interesting calibers of the day. All the Bru-ha-ha over "short mag" calibers was already done back in the 60's and 70's with the 284, 6.5 and 350 Rem. Mag. For my taste a flat Bolt beats the Round Bolt hands down. As far as a value for your 6.5 - it's hard to say. Surely one of the harder calibers to find I would consider a 90% gun just barely collecible and the price would reflect that - around $600. If it had iron sights (RS or S) and was in 100% condition in the box it may bring $1500. Sorely under-valued in my mind. And don't even bother looking in the Blue Book - they are WAY under valued in the REAL world.