I can see how someone might attribute the stay cap style to Araya, given their affinity for for it. However, the general style pre-dates Araya's usage, being very popular on a number of Italian brands. Also, as noted, it is to be seen on several early Univega. These Univega have serial number formats consistent with Miyata, a known Univega contractor. The caps would appear to be a standard, off-the-shelf frame fitting and not anything proprietary to Araya.
The T-prefix S/N on the 2nd Avalnche is the first direct tie I can recall seeing to Toyo for this format. Thank-you for posting. The format on the 1st Avalanche is consistent with that seen on Ritchey and Fisher. Still, its curious as to why they made such a radical change to the serial number format during this period. I'd also think that the annual volume for the Avalanche and Team Access alone would be close to, if not in excess of one thousands units, and that we'll eventually see some T8xxxx serial numbers.
The ES within the diamond is not a date code but the trademark of Eisho Seisakusho, a Japanese lug and bottom bracket shell manufacturer.
