Based on the Grandes Heures of Jean, Duke of Berry.
This is the second time I've used this source, and I had forgotten how INCREDIBLY PAINSTAKINGLY LONG it takes to paint.
Calligraphy was done by the most excellent Isemay the Nimble.[link]
It was for our outgoing baron at his devestiture, right before he moved far far away to another kingdom. He was one of the first people I ever met in the SCA, and he's like everyone's scadian big brother.
The miniature is based off of the fresco equestrian portrait of Guidoriccio da Fogliano, c. 1328-30, in Sienna:[link]