This is the World War II draft registration for Henry Brock [Harold's maternal uncle].
Here's a copy of the information about this document copied from ancestry.ca
U.S., World War II Draft Registration Cards, 1942
Name: Henry Brock
Birth Date: 10 Apr 1884
Birth Place: Warsaw, Poland
Residence: Kings, New York, USA
Here are my notes about this document:
Although the birthdate (April 10, 1884) is different from the one in Henry Brock's World War I draft registration (September 30, 1884), I believe this is probably the same Henry Brock, as his wife's name is Lea, they live in Brooklyn, and he's from Warsaw.
His employer's address is Creative Arts, 110 West 25th St. Previous documents about Henry show his occupation as "embroidery"; one can imagine that a company named "Creative Arts" might possibly have been creating embroidered items? (Henry's employer at the time of the First World War draft registration had been "World Art Embroidery Works.") See this address today in Google Maps.