Conn 28B Concert Grand
Date: 1928. Instrument owned by Paul Ayick.
Notice the lack of the right hand pinky ring common on instruments these days. Back then many instruments didn't have one. The 28B Concert Grand features a (in trumpet terms) massive #2½ bore (0.485").
What Conn said:
This trumpet has the largest bore of any of our trumpets and heavy gauge brass is used in its construction. It is especially designed for those "heavy" players who have been accustomed to "filling" a large bore and who desire an unusually big, powerful trumpet tone.
The richness and magnificence of its tone is really unusual and while the bore is large, it has a satisfactory resistance which just suits the "heavy" player. Its scale is even and flexible and for a trumpet of this size and bore, it is played with surprisingly little effort.
Many of these trumpets are being used in the larger symphonies and in military bands.
The instrument is 19½" long, weighs 2¼ lbs and has a 4 5/8" bell. Apparently the 28B is a "Low Pitch" version, the "High Pitch" version is called the 29B.