Wow - you can find a USA-made Acoustic amp for $5000? Even the "vintage" gear, while associated with Robbie Krieger's work with The Doors, and Jaco Pastorius's signature Weather Report-era tone, shouldn't be anywhere near that high. I'd be curious to know what you're seeing at that price.
For what it's worth, Steve Marks and his dad, I believe, founded Acoustic in the 1967, and the company folded in the late early 1980's or thereabouts. Steve Marks himself spent some time living in the Synanon community in the 1970's, and has gone on to own a litigation technology business.
The Acoustic brand was revived in recent years, although I have no idea whether Marks is involved, or if someone else bought the IP and other assets from him.