A set of open Roman caps that accompanied Rudolf Koch’s Fraktur typeface, Maximilian.
There are various digitizations, including versions by Keystrokes a.k.a. Fonts For Design (adding a solid cut), Dieter Steffmann (with ahistoric small caps) and CastleType (as Maximillian CT). Ambrose is a reworked version by Alan Meeks for Letraset. The sample shown here uses Maximillian CT.