I used the police chief of the town I live in. If you're in an unincorporated area, it would be the sheriff. It's just telling them who they need to "notify" about your new toy.I did the registration last night for a pistol with a brace that I had been wanting to SBR before this whole mess. The only thing I ran into that I wasn't sure about was the CLEO. I wasn't sure if for me, that would be Indianapolis Metro Police, or Indiana State Police. I did find the information on INGO that it appears to be ISP.
Hopefully I filled this all out correctly.