She is a kindergarten teacher at Seishou Academy under the elementary department. Her name "Thompson Sensei" was obviously derived from the M1928.

Type: Submachine gun
Place of origin: United States

Specifications
Weight 10.8 lb (4.9 kg) empty (M1928A1)
10.6 lb (4.8 kg) empty (M1A1)
Length 33.5 in (850 mm) (M1928A1)
32 in (810 mm) (M1/M1A1)
Barrel length 10.5 in (270 mm)
12 in (300 mm) (with cutts compensator)
Cartridge .45 ACP (11.43 × 23 mm)
Action Blowback, Blish Lock
Rate of fire 600–1500+ rpm, depending upon model
Muzzle velocity 285 m/s (935 ft/s)
Effective range 50 metres (160 ft)
Feed system 20-round stick/box magazine
30-round stick/box magazine
50-round drum magazine
100-round drum magazine
(M1 and M1A1 models do not accept drum magazines)