"International Working Men’s Association (IWMA)."

"
The U.S. ambassador and prominent scion of the presidential family informed the IWMA secretary William Cremer that the Address had been transmitted and received by Lincoln. The president willingly accepted the “sentiments” from “his fellow citizens” (Lincoln never forgot his political obligations even in a private letter!) as well as “friends of humanity and progress” globally.
"

https://www.friendsofthelincolncollection.org/lincoln-lore/marx-and-lincoln/

friendsofthelincolncollection org