[Boatanchors] Military Receiver R105A/ ARR 15 question

[Greg Mijal]

Hi:

I've been looking at an ARR 15 receiver listed on Ebay.  I'm thinking about mating it to my ART 13 for 75 M phone.
Ebay auction number is: 230 467 619 002

I'm not very familiar with this model and would like someone who has experience with it take a look and answer a couple of questions.
The right side widow looks like it is between bands.  Could this be normal or is something mechanically lacking?
Also, what is the purpose of the small left side window?
Thanks for your help
Greg
WA7LYO
Kinston NC