I found several photographs of my great-grandmother and her husband, on the back of which was printed:

Sgt. Flood Fishing and Hunting Club, Inc
For Men and Women

I've done a Google search, but can't find anything. Does this club ring a bell for anyone?

The NYS Department of State website includes a listing of all NYS corporations which lists:

Current Entity Name: SGT. FLOOD FISHING AND HUNTING CLUB, INC.
Initial DOS Filing Date: JUNE 16, 1948
County: BRONX
Jurisdiction: NEW YORK
Entity Type: DOMESTIC NOT-FOR-PROFIT CORPORATION
Current Entity Status: ACTIVE

There might be more information at the office of the Bronx County Clerk

Thanks - yet more proof that if you know where to look, you can find almost anything!