TRS-80 Model II 
26-6501 
TRSDOS-II 4.3


26-6501A.IMD
Application Processor
v4.3.11
3-21-83
Single-Sided
This is the production release master of TRSDOS-II ARCNET Application Processor


26-6501B.IMD
v4.3.11
Single-Sided
3-21-83
This appears to be a master release copy of v4.3.11 without ARCNET


ARC80AP.IMD
Application Processor
v4.3.11
Single-Sided
3-21-83
This is a reconstructed production master of 4.3.11 Application Processor by Aaron Brockbank


ARC80 A.P. 4.3.7 (SS)
v4.3.7
Single-Sided
2-11-83
Pre-release early ARCNET Application Processor


ARC80 A.P. 4.3.7 (DS)
v4.3.7
Double-Sided
2-11-83 (Labelled 4-21-83)
Pre-release early ARCNET Application Processor