I'm struggling to find the exact font that was used in the 1950s for International Harvester signage. Any help would be appreciated and I'm also open to similar font suggestions – particular focus on the 'R', 'W' and 'G' to closely match the original.

Just posting a bigger version of the top image, for better reference quality.

 

Edited February 9, 20242 yr by Bjørn Edvard Torbo
increased resolution

There is no reason to believe it matches any specific typeface, as typefaces at that time were made almost exclusively for printing. Signage was usually custom work only loosely based on print font styles. 

However, the general style in those pictures is present in fonts like Gills Sans and Johnston. More similar fonts here. 

Thank you @Ralf Herrmann – this was really helpful 👍 

The R and the W are closer to Futura than to Gill Sans, I think, but the G doesn't quite match Gill Sans or Futura or Johnston.