Grove Valves or Grove Italia as I know them, I think they were taken over my Dresser some years ago.  Try looking on a Dresser Web site.

The website you need is www.dresser.com.
Good Luck!

Grove Valve is out of business, but try www.mwvalve.com
for Midwest Valve.  They may be able to assist.
See note below on Grove Valve.

EmeryTech Center (Grove valve)
1400 64th Street

The Grove Valve building was a center of heavy industrial activity since 1939, most recently housing Grove Valve and Steel until 1996. Grove Valve was a manufacturer of large engineering valves used for industrial purposes. The Grove Valve building, located at 1400 - 65th Street, will be remade as the EmeryTech Center with over 230,000 square feet of office space. The development is being anchored by the corporate offices and warehouse space for Andronico's Markets, Inc., a high-quality Bay Area supermarket chain, which will occupy approximately one-third of the building. The historic facade of masonry base and glass and steel sash window walls will be largely retained. While the departure of Grove Valve's 100 jobs was a tremendous loss for the City, the new EmeryTech Center is expected to house approximately 600 jobs.

J. Alton Cox
President
DeLuca Test Equipment
www.delucatest,com

The type G4N is definitely a Grove Italia valve design designation.

Grove were bought by Dresser who were subsequently bought by Haliburton. Now trading as Dresser Flow Control.

Contact Dresser Flow Control at Houston Texas

Grove has three manufacturing facilities around the world. The Grove valve line is manufactured under the Dresser Flow Control name. I personally work for the Canadian manuafacturing arm of Dresser Flow Control. Listed below are the Grove manufacturing facilities complete with contact information:

Dresser Flow Control Grove Canada  
(866) 789-0001

Dresser Flow Control Grove U.S.
(281) 568-2211

Dresser Flow Control - Grove Italia
39-0383-6911

Any questions , please call
Jim Dietrich
Project Sales Manager
Dresser Flow Control - Canada