Today I was looking around for more v7 stuff of interest that I might find on the web and came across a tape image in the ATT bits directory: http://www.bitsavers.org/bits/ATT/ labeled X7252.2015_UNIX_V7.tap and an image of the reel with original and added markings. I downloaded it and sure enough, it's a bootable v7. I then compared it with my recreated tape image from the files in the Keith Bostic folder on tuhs. The 11.7MB tapes are nearly identical, with only a handful of bytes that differ at the very end of the tape:

ATT tape:
54532000    000000  000000  024000  000000  000000  000000  000077  000000
54532020    052135  014020  010000  034113  056720  023524  072143  122062
54532040    141401  000000  000000  000000  000000  000000  000000  000000
54532060    000000  000000  000000  000000  000000  000000  000000  000000
54532100    000000  000000  000000  000000  000000  000000  000000  037400
54532120    000000  000000                                                
54532123

Bostic recreated tape:
54532000    000000  000000  024000  000000  000000  000000  177777  177777
54532020

I'm wondering - 1) Does anyone know the provenance of the X7252.2015_UNIX_V7.tap 2) Do the bytes at the end of the tapes look familiar or particularly meaningful? My knowledge of 40+ y.o. tape formats is woefully lacking, but I'm curious.

Will