Tell me more! Help Needed with a Kepi!

[HatEnjoyer]

Hello all! A friend of mine has been reading about the Indian Wars and is looking to acquire an M1872 Kepi for his collection of military antiques. The hat itself looks fine but he's puzzled by the company letter "G" on the front. Does anyone know if it's original to the hat? I'm thinking not, but I don't collect Indian Wars. Thanks in advance!

 

[RedRover]

 

[Salterr]

What's the size of the letter and what fasteners does it have?