I'm assuming this is a made in USA one? From the make tag it looks to be the older ones. PRL were made in their own US factories from 70's to 90's until Corn. picked up the invoice. Just yesterday, Orgetorix posted the union make tags to their corresponding years.
Scroll down to the bottom for those info.
Regarding your over sized pants, I soooooooooooo regret not picking up some recent MTM Sammy pants for bigger boys, size 50.
I should say (and I need to put this over on the other thread) union tags are helpful, but they are only a general guide. Earlier tags were sometimes used after their replacements had been introduced if a particular tailor or factory had a bunch of the old ones laying around. The only thing a union tag will tell you for sure is that the garment wasn't made prior to when they started using that label.
In other words, you can use a union tag to establish a not-earlier-than date of manufacture, but not a precise date or a not-later-than date.