Just aquired a fantastic shape vintage AMPEG SVT Blueline. Curious as to what year the experts think this amp is? Here are some other interesting features: - GE6550 USA Power Tubes - GE Tubes in the lower chassis as well. - Appears like the preamp tubes are a combination of old tubes (havent taken them out yet to fully confirm) - Two prong power - All the weird screw heads - an original, "hard wired" speaker cable. Aparently was only changed the end from 4 prong to 1/4" - Unique band logo on top "Rockestra" - Both transformers appear original, one has "Hammond" on it. saw a similar example on ebay with same part numbers - fan updated - original tolex, etc. In any event, very quite at idle, with a hint of occasional microphonic ring when turned up. Sounds amazing when running full!!!! Worth it. Also in pic is my stock 1961 Navy Flair Ampeg B15 to match for a heavenly combo. Any input greatly appreciated!!!