I've been trying to find some information on the Internet on this wiring device manufacturer but nothing comes up.
Their name appears a lot on those miniature cord-switches for SPT-1 lampcord (with the insulation-piercing points and the two halves that you screw together).
On some really old lamps I've seen one type called the "Shockproof" switch, which uses two metal clips to clamp the two halves of the shell together, instead of a screw through the middle.
Gilbert also makes/made a type of ez-on two-pin cord cap for SPT-1 cord where the wire was inserted into a little groove on the shell of the plug and a cover slides into place.
I haven't seen new Gilbert-branded cord-switches in the lighting-parts stores in my area but the plugs are sold in various colors (black, brown, gold, ivory, white) and in polarized and un-polarized configs.
There is also a mating cord-connector.
I assume the company -- or at least the name -- still has to be in business otherwise every single lighting store in New York City wouldn't be selling them....
Unless there is a massive warehouse somewhere with boxes and boxes - MILLIONS of these things sitting in there and these places have been trying to get rid of them for YEARS!
Also, who recognizes another NYC-based brand of devices (mostly lampholder clusters and individual lampholders) called 'Triboro.'?