It doesn't seem that anyone's mentioned this before...
"Keystone Shortway" is little more than a seldom-used nickname anymore, although it is still signed in at least one location. I took the picture below on Tuesday just NE of Exit 192 near Loganton. This auxiliary plate has remained despite the junction plate and 80 shield having been replaced by newer pieces with prismatic sheeting. The Shortway plate has the old PennDOT steering wheel-like logo, so my guess is that it was installed just after the department was created in May of 1970 in time for the opening of last I-80 segments in October of that year.
I believe I've seen a couple more of these not far from this one (maybe Milesburg or Bellefonte), but I'm not sure. I have to wonder if these were once more common across the state and if there was any more Shortway signing in the past.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fbriantroutman.com%2FResources%2Fi-80_keystone_shortway.jpg&hash=0963fb98cb9000bf53dde3b834fd10b1a73eaf82)
This is sort of like Ocean Highway seldomly signed along US 13 anymore on the Delmarva Peninsula. Technically US 13 from the Delaware Memorial Bridge to Hampton Roads Area, along with US 17 southward to Jacksonville, FL and a piece of US 40 to connect with US 130 northward to North Brunswick, NJ is the Ocean Highway. MD and VA were the last to refer to it as such, but now its almost extinct in the sign field all together.
When I was on US 13 back in 02, there was one sign left just south of DE-MD 54 on the first US 13 SB reassurence shield in Maryland.
I noticed between the mid-1990s and the mid-2000s that the Keystone Shortway banner became even more endangered.
I checked The Story of the Keystone Shortway book, but there is no mention of the banners or whether they were along the entire route or just around central Pennsylvania. The latter may be true because the Keystone Shortway Association was based in Williamsport.
I've found at least a half-dozen of them on intersecting routes, mostly in west and central PA.