I want to say more or less minor league caps followed the same lineage, if not for a one or two year lag. I wouldnt doubt some teams had wool caps well into 2010 (minor leagues went poly and black underbrim the same time as MLB). I just recently bought some Great Lakes Loons hats from their official store, and they were still selling some 2006 white sweat band (blue NE tag) 100% wools. So the lag is definitely a real thing
Here is one minor league hat with what I believe to be 2002-2004 era
This one too around the same time as above
Here's another AAA minor league hat
Based off of MLB on fields, its around a 1989-1991 model.
This one, around 1995.
Hard to see but it has the older 5950 spelled out. Its identical to a '95 Indians on field that I have, in regards to tagging.
From another minor league hat
This one 97-99 ish
It actually features a NE flag on the side
Speaking of minors, does anyone know when the NE flag was added to the side? Looking online for various tags, I found the one above going back some 20 years. The ~1995 era on fields did not have the flag. The ~1997-2000 ones did. So I guess within that time frame, the minors made the switch.
I guess we have to be lucky it took 20 years for the Majors to get the flag treatment.
I also have minors that have the fly your own flag marking from the past few years, as well as a black under, with the blue and white NE tag (2007ish). So for the most part, minors have followed the MLB lineage almost to a tee.
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The real trickery is these fashion caps by NE. Even the made in china customs that I have. The tags are all over the place. There is zero indicators on age of when they were made. But for the most part, minors and majors have some similarities. On ebay, they are usually cheaper too. You can get some gems on ebay for sure of vintage minor league hats... Then there are some sellers who mark them as vintage, but they are black under, and have pretty current markings.