Refer to the AR-A/AR-B/AR-D series catalog excerpt, which has been reproduced below.
The part numbers of standard AR20 to AR60 round type pressure gauges are “G36-10-01” and “G46-10-01”(for the R thread type).
For example, the part number of the AR30-03BG-A pressure gauge is “G36-10-01.”

Body Size: 30, Backflow: w/o Backflow Function, Thread: F (G), Port Size: 03 (3/8), Options: w/o Mounting Option, Set Pressure: 0.05 to 0.85 MPa Setting, Exhaust Mechanism: Relieving Type, Flow Direction: Left to Right, Knob: Downward, Pressure Units: Unit on Product Label: MPa, Pressure Gauge in SI Units: MPa

Size: 3/8, Reverse Flow: Regulator, Standard, Thread: G, Port Size: 3/8, Accessory: None, Option 1: 0.02~0.2MPa Setting, Option 2: -

Size: 3/8, Reverse Flow: Regulator, Standard, Thread: G, Port Size: 3/8, Accessory: None, Option 1: Non-relieving, Option 2: -

Size: 3/8, Reverse Flow: Regulator, Standard, Thread: G, Port Size: 3/8, Accessory: None, Option 1: Non-relieving, Option 2: R+Y

Size: 3/8, Reverse Flow: Regulator, Standard, Thread: G, Port Size: 3/8, Accessory: None, Option 1: None, Option 2: Upward Handle

Size: 3/8, Reverse Flow: Regulator, Standard, Thread: G, Port Size: 3/8, Accessory: None, Option 1: Non-relieving, Option 2: Upward Handle

Size: 3/8, Reverse Flow: Regulator, Standard, Thread: G, Port Size: 3/8, Accessory: None, Option 1: None, Option 2: R+Y

Size: 3/8, Reverse Flow: Regulator, Standard, Thread: G, Port Size: 3/8, Accessory: None, Option 1: 0.02~0.2MPa Setting+Non-relieving, Option 2: Flow Direction: Right->Left

Size: 3/8, Reverse Flow: Regulator, Standard, Thread: G, Port Size: 3/8, Accessory: None, Option 1: 0.02~0.2MPa Setting+Non-relieving, Option 2: -

Size: 3/8, Reverse Flow: Regulator, Standard, Thread: G, Port Size: 3/8, Accessory: None, Option 1: 0.02~0.2MPa Setting, Option 2: Flow Direction: Right->Left

Size: 3/8, Reverse Flow: Regulator, Standard, Thread: G, Port Size: 3/8, Accessory: None, Option 1: 0.02~0.2MPa Setting, Option 2: Upward Handle

Size: 3/8, Reverse Flow: Regulator, Standard, Thread: G, Port Size: 3/8, Accessory: None, Option 1: None, Option 2: Flow Direction: Right->Left

Size: 3/8, Reverse Flow: Regulator, Standard, Thread: G, Port Size: 3/8, Accessory: None, Option 1: None, Option 2: None, Made to Order: For High Pressure

Body Size: 30, Thread: F (G), Port Size: 03 (3/8), Option: w/o Mounting Option, w/o Pressure Gauge, Semi-Standard: Standard

Regulator, Pressure Boosting Valve: Regulator, Regulator Type: Standard, Shape: Standard, Operating Environment: Standard, Compatible Fluid: Air, Exhaust Mechanism (Air Bleed): [Included] Relief, Reverse Flow Function (Relief): No, Supply Side Connection Type: G, Supply Side, Connection Diameter: 3/8, Flow Direction: [Right] From Left to Right, Control Side Connection Type: G, Control Side

Regulator, Pressure Boosting Valve: Regulator, Regulator Type: Standard, Shape: Standard, Operating Environment: Standard, Compatible Fluid: Air, Exhaust Mechanism (Air Bleed): [Included] Relief, Reverse Flow Function (Relief): No, Supply Side Connection Type: G, Supply Side, Connection Diameter: 3/8, Flow Direction: [Right] From Left to Right, Control Side Connection Type: G, Control Side

Assembly Environment: P (Clean Room), Operation: 0 (Automatic Operation Type), Connection Size: F03 (G3/8, G1/4)

Assembly Environment: Ordinary Environment, Operation: 0 (Automatic Operation Type), Connection Size: F03 (G3/8, G1/4), Option: B (Foot)

Assembly Environment: Ordinary Environment, Operation: 0 (Automatic Operation Type), Connection Size: F03 (G3/8, G1/4)