What you are defining as "transitional" are major, in most cases completely different, design changes. I, and many others I suspect, use "transition" in regards to a perhaps minor change of a design type on a master hub or master die, that presents itself across many working dies, and often including multiple mints. It has persistence beyond a "variety", like an RPD or DDO which is restricted to a single die. Such changes most often continue from one year to the next and beyond, and are widely recognized as "types", and considered transitional in their first year. For an example most familiar to me, the addition of an extra fold in the right ribbon on the reverse of Barber dimes occurred in mid-1901 and is documented as a separate type in all guidebooks. Both the earlier and thick ribbon types occurred in 1901, and in subsequent years the thick ribbon was the standard type through the end of the series. However, both types were still minted in San Francisco through 1905. I consider all of those SF anomalies to be transition varieties, and what makes them collectible/interesting is that they're not the expected type.
You may be misinterpreting my Barber quarter example, because it is not really known outside of subscribers to the BCCS journal. Yes, obverse and reverse design changes occurred in 1900 that are currently documented as obverse 1 and 2, and reverse 2 and 3, respectively, and those new types continued on from 1900 forward to the end of the Barber quarter series. I assume this is what you mean by a "year variety and use after." However, there is an intermediate obverse type involving the letters of In God We Trust, recently discovered (by me), that only existed in 1900. That's what I was referring to as a transition type occurring within a single year. I believe this hub/master type produced working dies only between May and October 1900, and I estimate over 5 million coins used it across all three mints. The type is not found in 1901 - thus a transition within a single year.
I'm not sure exactly how this relates to the SMS discussion, but I think how one defines type, transition, variety, etc, is influenced by how interesting it is to a particular collector. For example, 1916 was a transition year for dimes, but I don't think of either the 1916 Barber or 1916 Mercury as "transitional" from the standpoint of interesting or collectible. It's odd to have two completely different designs in a single year, but the coins themselves aren't anomalies or uncommon.
You may be misinterpreting my Barber quarter example, because it is not really known outside of subscribers to the BCCS journal. Yes, obverse and reverse design changes occurred in 1900 that are currently documented as obverse 1 and 2, and reverse 2 and 3, respectively, and those new types continued on from 1900 forward to the end of the Barber quarter series. I assume this is what you mean by a "year variety and use after." However, there is an intermediate obverse type involving the letters of In God We Trust, recently discovered (by me), that only existed in 1900. That's what I was referring to as a transition type occurring within a single year. I believe this hub/master type produced working dies only between May and October 1900, and I estimate over 5 million coins used it across all three mints. The type is not found in 1901 - thus a transition within a single year.
I'm not sure exactly how this relates to the SMS discussion, but I think how one defines type, transition, variety, etc, is influenced by how interesting it is to a particular collector. For example, 1916 was a transition year for dimes, but I don't think of either the 1916 Barber or 1916 Mercury as "transitional" from the standpoint of interesting or collectible. It's odd to have two completely different designs in a single year, but the coins themselves aren't anomalies or uncommon.



















