This is the World War I draft registration for Harry Rosenthal (the son of Leah Rosenthal) [Harold's cousin].
Here's a copy of the (modern) transcription copied from ancestry.ca
U.S., World War I Draft Registration Cards, 1917-1918
Name: Harry Rosenthal
City: St Paul
Birth Date: 4 Mar 1896
Draft Board: 04
Here are my notes about this document:
The place of birth, Prashniz, is the same as the place of birth given in Albert Rosenthal's naturalization documents and in the 1902 ship's manifest (though with different spelling each time -- I believe these are variant spellings for the Polish town of Przasnysz).
If Harry's date of birth as given here (March 4, 1896) is correct, then the ship manifest saying he was 5 in December 1902 would be slightly incorrect, as he would have actually been 6 at that time. (On the other hand, the entry for Harry Rosenthal in the Social Security Death Index says his date of birth was March 4, 1897.) The draft registration of June 5, 1917 was a registration of men aged 21 to 31. If Harry was born in 1896, as this draft registration form says he was, he was 21; but if he wasn't actually born until 1897, that would make him only 20, too young to register.
Harry's occupation is given as soft drink manufacturing; he is self-employed.
He is single.
For the question "Do you claim exemption from draft (specify grounds), it looks like he originally replied "None" but then that was crossed out and replaced with "Business responsibilities."
His address in St. Paul is 358 Smith (North?), which is the same address as that given on Albert Rosenthal's draft card (Harry's uncle's). See this address today in Google Maps. So presumably Harry, Albert, Naomi, and young Harold were all living together.