When/why was “T Swiss Made T” used?

[Zinchin]

I’ve come across a few charts over the years that reference “Swiss T-<25”, “T Swiss T”, etc. but the one that I was always curious about was the “T Swiss Made T” notation. I believe the first two listed are different based on radioactivity numbers, but not sure why the difference between “T Swiss T” and “T Swiss Made T”. It seems to have been used in the same date range so why the difference? Was it specific to country codes, models, etc.? Curious any info you guys can share.

Thanks!