SNG Online is a godsend, I use it all the time (usually for
Lockett, but some other useful
collections from the UK series are up too).
Sometimes they include a note indicating where
Lockett purchased the coins (e.g., most of the
Bement or
Pozzi coins are noted as such), but not in this case.
The British Numismatic Society published
Lockett's notebooks of purchase records not long ago:
https://www.britnumsoc.org/275Very detailed, often much more so than other sources (especially for the Greek bronzes), occasionally with a photo clipped out (I think the photos are usually from catalogs he purchased them from, e.g.
Bement or
Pozzi, though I try not to think of Naville-Ars Classica catalogs being cut up for one's notes!). I've been able to find virtually every coin of
his that I've tried to look up.
This coin was in "Volume 43: Greek 5 AR
Russia to
Euboea."
Unfortunately, nothing too exciting, one of the thousands he bought from "Baldwin" with no further detail:
Nonetheless, another useful source if you have any interest in
provenance research and/or have an ex-Lockett in your
collection. (It includes all the bronzes, too, individually labeled. Bronzes weren't in
his SNG. Many of them include detailed descriptions & provenances not indicated in the Glendining sales, which lumped them in groups, often noting only
mint & era. A great many are ex-Lord Grantley, many
Rev. Rogers, Pierre Straus Coll.,
Pozzi, and so on.)