Very nice example, just came on the market in September 2016 through vintage dealer Guitar Point in Germany with an asking price of 3,250 Euro. Of note, it looks like the volume and tone knobs are slightly different from OEM stock, as they appear to attach with set screws. Non-original truss rod cover, but if you're patient you can probably source an original one on eBay. Interesting that the pickup is stamped 'CB' on both ends - never seen that before. And although we can't be 100% sure, it looks like the felt washers under each of the three strap buttons are missing. Highly unlikely to have been lost along the way, possible just an assembly oversight back in 1970.
1970 Dan Amstrong (Ampeg) Plexi/Lucite Guitar incl. black hardshell case
"Clean 1970 Dan Amstrong Luthite guitar in excellent condition for its age. Only a small number of this Instrument has been built from 1969-1971. They chose lucite as a alternative body material for extanded sustain, another feature has been the interchangable pickup. Many famous players as K. Richards or The Georgia Satellites have played this instrument for its special sound, great for slide-guitar. Excellent playability, the original frets are still in perfect shape. Comes with a black hardshell case w/red interior."