FYI, It appears that QF-2G and QF-2G1 are the same (
Full catalogue):
page 27
Model No: QF-2G
Nominal pressure PN(Mpa) 15
Nominal diameter DN(mm) 4
structural style AXIS
Working medium O2, N2,Air
Outlet thread size(mm) G5/8 Female thread
Inlet thread with cylinder(mm) GB8335 PZ27.8
Working pressure for inner safety device 18~22.5Mpa
Model No: QF-2G1
Nominal pressure PN(Mpa) 15
Nominal diameter DN(mm) 4
structural style AXIS
Working medium O2, N2,Air
Outlet thread size(mm) G5/8 Female thread
Inlet thread with cylinder(mm) GB8335 PZ27.8
Working pressure for inner safety device 18~22.5Mpa