The name of the recipient is not written on the flag, but a Shinto priest 立崎（龍？）一郎 Tatezaki/Tachizaki (Ryū?)ichirō wrote a Japanese poem on the upper right corner. He is a priest of 国幣中社貫前神社 Kokuhei Chūsha Nukisaki Jinja, i.e., 一之宮貫前神社 Ichinomiya Nukisaki Shrine in Tomioka city, Gunma prefecture, and the shrine's seal is put there, so the recipient might live around the city. There are also two company's names 株式会社吉田組 Yoshidagumi Co. Ltd. and 株式会社早津組 Hayatsugumi Co. Ltd. These names are common as a construction company.
Some other people advised this... 武運長久 Buun (Fortunes of war) Choukyuu (Forever/perpetually) usually translated as "Eternal Good Fortune in Battle" or something similar. Sometimes 祈 is added to make it Ki Buun Choukyuu "Prayers for Eternal Good Fortune in Battle"" This is at the top
The recipient Shirakawa Rokuro's flag was signed by two company presidents.
Yoshida Union, LTD. (possibly a construction company)
Shachō Yoshida ...
I cannot read the name of this Union (ergo the pink color); HOWEVER, I'm guessing it is named after its president Yoshida, and make that assumption based on the Union named on the left side of the flag that I can read.
Interesting in that ~君 (~kun/Mr.) is not appended to Shirakawa's name.
Far right side:
Hayatsu Gumi, LTD.
No date on the flag as far as I could see.
No need to try to parse Inoru(Ki) Buun Chōkyū any further. Its just a set phrase, an idiom: Good luck in battle. Probably the most common phrase on these kinds of flags. With or without the 祈, the meaning is the same.
I wouldn't assume Shirakawa Rokurō is the recipient because of the fact the honorific is left off. Rather, Shirakawa Rokurō is probably someone working at the factory. The recipient's name would certainly have some honorific attached to it.
~gumi is a common way to represent construction companies, as Toritoribe-san said. It isn't a specific labor union. There is a different word in Japanese for "Labor union".
So, this is simply a flag that was presented on behalf of two construction companies, with signatures from various employees of the companies.