Refers to the scale or design iteration. In Stuarts’ internal numbering:

A minor but welcome change: the stock binding posts have been replaced with Rhodium-plated Tellurium Copper units from Furutech. Internal wiring is now a continuous run of proprietary OCC (Ohno Continuous Cast) copper, silver-soldered directly to the drivers—no more push-on terminals.

If you’re a completionist or an investor in rare art toys, the Glimpse 28 Alpha 4 with the 2024 upd is a blue-chip asset. Its value has increased ~40% since the upd was released. However, hunting for it requires:

Beware of listings that say "Roy Stuarts Glimpse 28" but omit "Alpha 4" or "Studio C 2024 upd"—those are likely later Beta runs or recasts.