If you order an A77VG020 or A77VG020A, you will get the entire gas train. This includes part 96SD012 which is the on/off Dual Shutoff Valve from Dungs. On the bottom of this valve there are two ports. As a part of the gas train there are two visual indicators in those ports. When the valve by itself is ordered, there are no visual indicators in those ports and there is just the plugs.

The procedure given by Dungs is as follows:

1. Remove the plugs and the o-rings on the bottom of the valve with a 5mm hex key wrench.
2. Insert the visual indicator and its o-ring; using a 5/8" (16mm) open end wrench, turn clockwise until the visual indicator is sufficiently tightened. DO NOT overtighten, or the o-ring can be damaged. An additional 1/8 to 1/4 turn after finger-tight is typically sufficient.
3. Before placing the valve into service, test the indicator by opening and closing the valve to visually verify the indicator is working properly.
4. Apply a soapy water solution between the indicator and the valve body to verify that no leakage appears.

The old visual indicator should be removed from the valve body and using a new o-ring, inserted into the new valve body. If the old visual indicator can not be used, Milnor stocks the visual indicators under part number 96SD014.