I came across this article from GoPSUSports.com today highlighting how the Penn State uniform has changed (or more accurately hasn't changed...much).
A few months ago we had a post of the image of the "new" uniform was released. I remember asking what time period our new uniforms were most like, and iIRC through multiple google image searches we arrived at Late 60's/Early 70's minus the numbered helmets (and late 70's if you want to include the unnumbered helmet). The article pretty much confirms that, except there is an early manifestation of the non-striped/bordered uniform that predates our estimate by 30+ years:
That is Leon Gajecki, a letter winner at PSU from 1938 to 1940. Obviously we can't really tell if there's a number on his helmet, but (and perhaps Derry can confirm for us) this period may have just had leather helmets until the dawn of the plastic helmet (from what I can find on the interweb, the NFL switched in 1949 to plastic helmets, so I'm assuming college followed suit).
I don't want to steal too many great photos from the article, but this one is quite possibly my favorite. This is PSU's first and ENTIRE 11 man football team in 1887:
"Take your 85 scholarships and SUCK IT"
I should really also add, especially if this sort of thing interests you: if you haven't been to the All-Sports Museum in Beaver Stadium (and I don't know why you haven't because I really, really, really recommend it for any PSU fan), I highly recommend it. Pictures are one thing, but you get to see the history of PSU athletics first hand. We're also extremely lucky to have a university with a very deep archive of historical photos and artifacts from our past that remind us just how far Penn State has come in it's 156 years.