Elgin Grade 387 With An Odd Bushing

You never know what you're doing to find when you get into a watch...  Here's what I found on removing the dial from this one.  At some point in the past a really large piece was cut out of the bottom plate, where the lower balance jewel mounts.  I round piece of brass has been fit there like a sort of giant bushing.  I'm not sure what problem would prompt this...  

This watch is an Elgin grade 387. It's a 16 size, 17 jewel movement, made about1914. 

The case is a slightly unusual, for a 16 size watch, swing-out type.