It could also be a Bourns PEC11
From the data sheet...
PEC11- 4 0 20 F - S 0012
PEC11 = Model
4 = PC Pin Horizontal/ Rear facing
0 = Detent option
0 No Detents
1 28 Detents (18 pulses)
2 24 Detents (12, 24)
3 12 Detents (12)
20= Shaft length mm 15,20,25,30
F= Shaft style (F for Flattened, K for Knurled)
S = switch , N = no switch
0012 = Resolution (number of pulses. 0012, 0018, 0024)
Hope this helps
Royce