So, I came across this tape:

http://bitsavers.trailing-edge.com/bits/DEC/pdp11/dectape/TU_DECtapes/unix6.dta

I was curious what was on it,  so I read the description at:

http://bitsavers.trailing-edge.com/bits/DEC/pdp11/dectape/TU_DECtapes.txt

UNIX1       PURDUE UNIX TAPES
UNIX2
UNIX4
UNIX6
HARBA1      HARVARD BASIC TAPE 1
HARBA2      HARVARD BASIC TAPE 2
MEGTEK      MEGATEK UNIX DRIVER
RAMTEK      RAMTEK UNIX DRIVER

Cool, sounds interesting, so I downloaded the unix6.dta file and fired 
up simh - after some fiddling, I figured out that I could get a boot 
prompt (is that actually from the tape?) if I:

set cpu 11/40
set en tc
att tc0 unix6.dta
boot tc0
=

At that point, I was stuck - the usual tmrk, htrk, and the logical 
corollary tcrk didn't do anything except return me to the boot prompt.

I was thinking this was a sixth edition install tape of some sort, but 
if it is, I'm not able to figure it out. I thought I would load the tape 
into v7 and look at its content using tm or tp, but then I realized that 
I didn't have a device set up for TU56 and even if I did, I didn't know 
how to do a dir on a tape - yeah, I know, I will go read the manual(s) 
in chagrin.

In the meantime, my question for y'all is similar to my other recent 
questions, and it goes like this:

When you received an unmarked tape back in the day, how did you go about 
figuring out what was on it? What was your process (open the box, know 
by looking at it that it was an x rather than a y, load it into the tape 
reader and read some bytes off it and know that it was a z, use unix to 
read the tape using tm, tp, tar, dd, cpio or what, and so on)? What 
advice would you give a future archivist to help them quickly classify 
bit copies of tapes :).

Thanks,

Will





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