From this link it's inferred that the DAC-08 was from 1974...
http://smithsonianchips.si.edu/augarten/i42.htmIf that is the case that makes it something like 45 years young! Not many valves/tubes had a production run that long, there are exceptions, say the ECC83/12AX7, still in production, but in quantities of far less than 1% of the 50s & 60s...and often from dubious sources...yet still hideously overpriced...
If you click the Index on that page there's a whole lot of other chips most of us older guys have forgotten about, sometimes with good reason...and the younger have never heard of...and good luck in getting hold of any...
Steve A.