Gray's plant is likely "Charity" mahonia x media.
The story behind 'Charity' is also filled with intrigue. 'Charity' is a hybrid of M. japonica and M. lomariiflia which showed up around 1950 or '51 in a shipment of 100 M. japonica seedlings from Slieve Donnard Nursery of Northern Ireland. Six of those seedlings eventually found their way to the Savill Garden near Windsor, and several years later when they eventually flowered it was obvious that one plant was markedly different from the others. The new specimen was subsequently identified as a naturally occurring cross between the two species, stock plants of which were grown in close proximity at the nursery.
http://www.swansonsnursery.com/blog/2015/01/16/virtues-of-charity-mahonia
I have three of these as part of my winter garden. They haven't filled in yet so they look a little funny, but they are absolutely delightful when everything else has given up. I'll post a pic from Nov 3rd, 2016. For a couple of weeks after that I had a few straggler
bees feeing off of these. I think they must have been one of the last few food sources available...in my
yard, at least. They are VERY spiny, moreso than the
native mahonias. One of the other reasons I have planted them as part of a hedge is to provide safe cover for birds. The birds really like my mahonia aquifolium....too soon to tell with these.
The berries look similar and have about the same quality of taste, LOL.
Oh, one other function of this mahonia....it grows where plants should not really grow. This section of my yard is basically really the edge of the neighbors driveway and these are essentially planted into shale-like driveway gravel. I mulch them well and say nice things to them. but they are growing as if they are happy in soil that could only be made worse if I poured a bottle of motor oil into it and lit it on fire. Tough, tough plants.