A doubt: Number 79 on Rolling Stones' t-shirts

Hi, just a simple question for Rolling Stones fans and people who know about music in general.

Why do some The Rolling Stones' t-shirts have the number 79 on it? Have you seen these? Are they popular in your country?

Here in South America are quite popular. I can't find out where this trend started.

I tried Google, but I couldn't find anything... Thank you!

Never saw one of these. Do you have a picture?

Hi, thanks for replying!

Check this link:

Thanks anyways, it's also good help to know that it isn't popular in your country.

I've been searching and I'm almost sure it is something that came out in Argentina around 1995 (I'm from Uruguay, right next to it, in South America).

Anyways, if you have any clues...