Dye sublimation quality: Model F > IBM Model M(metal logo) > Lexmark Model M(Grey logo) > IBM Brother buckling spring keyboard
Model F having the perfect all black Dye sublimation but not double-cap. IBM Model M(Metal logo) is the best quality on double-cap.
PBT plastic quality: Model F = IBM Model M(metal logo) > Lexmark Model M(Grey logo) > IBM Brother buckling spring keyboard
The IBM Model M(metal logo) did the work to prevent the deformation on the keycap(pic5) but the Model F didn't.
01_Top of keycaps

02_Upperside keycaps

03_downside keycaps

04_left side keycaps

05_bottom of keycaps
