I think it's because they were not fancied by hams, so they largely survived the era. For example, at NEAR-Fest this weekend there were at least 4 pristine ARC-12 units, and essentially nothing ARC-5. FWIW, -John David Stinson wrote: > It's too bad the Type 12 doesn't get more attention. > It's an exceptional set, and inexpensive. >