Fairmount 9/16 x 5/8 Open End Wrench (535-OW)

Fairmount 9/16 x 5/8 Open End Wrench. How old is this? Well, my great grandfather bought this deal from the US government I don't know how long ago, and they have been sitting in a box in the basement ever since. Surprisingly little rust on them. Beefiest open end wrench I've ever seen. 8 1/2" Long. - Fairmount 9/16 x 5/8 Open End Wrench///brand_for_product_detail=Fairmount,close_out=Yes,companydescription=Fairmount - Made in the USA,condition=New,condition_google=new,cost=0.500000,countrymade=Made in the USA,country_flag=no_selection,featured=0,flag=no_selection,identifier_exists=0,instock=in stock,is_recurring=0,listprice=10.00,madeinusa=1,manufacture_country=United States,product_image_size=Default,product_page_type=Default,sellprice=10.00,smart_campaign_bestsellers=Smart Campaign Bestsellers,square_product_image=https://square-production.s3.amazonaws.com/files/94fdb05754b040f10969c3230a822f0048ba3123/original.jpeg,store_price=10.000000,sw_featured=No,sync_update_msg=Modified in Magento by harryepstein on 30/03/2017,url_path=fairmount-9-16-x-5-8-open-end-wrench,warehouse=B2 03 L 04