I don't think you can read too much into historical label details for several reasons:
branding wasn't as rigidly controlled in the 70s, 80s and 90s as it is today, certainly not for small companies, so variations would have been normal
you are talking small jobbing printers so different printer or even print run = label variant. These things weren't based on digital files and digital printing in the same way as they are now
you can't assume that one batch of labels was used up before another was started or that there was only one batch on the go