Seeing any of these products outside the shop, you’d never know Etna made them. Mr. Galuppo did not use a signature or identify his clients, a tradition Ms. Galuppo continued in conversation.

Some customers wanted to prevent the competition from learning about their suppliers. Others, especially the “big architects” — “You would know their names,” Ms. Galuppo said — might have suggested they made products in-house that actually came from Etna.

As a result, the business was more influential than widely known. Consider the tattoo industry. Michelle Myles, the co-owner of Daredevil Tattoo and its Tattoo Museum, along with employees at Fineline Tattoo and Fun City Tattoo, two of the oldest parlors in New York, all said that the city’s largest supplier of tattoo equipment was Unimax Supply Company, and that they had never heard of Etna Tool & Die.

But Wes Wood, 77, the founder and owner of Unimax, said that as his business grew, he started to get 90 percent of his equipment from Etna — all of the tubes, frames, grips, springs, and needle bars that make up a tattoo machine, the remains of which still litter 42-44 Bond.

By the 1980s and 90s, industry was vanishing from NoHo. The neighborhood became associated instead with artists and punks, represented most famously by CBGB. Tattooing remained illegal until 1997, but that did not scare away Etna, which adapted to the times. At one point, Mr. Wood said, every tattoo parlor in New York was using gear made by Etna.