Yes - 67 was only Trico.
not sure about 68
69 started the Made in USA.
now to be perfectly honest most can't tell the difference, or can't see the difference.
And unless you are being judged by Bloomington Gold or NCRS with your Corvette. - I wouldn't sweat it.
Last time I sold a set of the <Trico> blade holders for 67, I think a 67 Corvette guy gave me $375 for the pair.
Lucky I had an extra set, or I may have considered selling them off my car.