I ran across an early GLM Model 17 pump that has an external box mounted on rear skin. This appears to be original since the rear skin has been shaped to accept this box. The bottom of box has rusted out and you can see two holes that are through the rear skin.
I have seen in Jack's 2cnd edition gas pump identification book, page 173, it appears that the 1921 year with totalizer had this box.
Can anyone tell me what this box was for?
See pictures.
Any help is appreciated.

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