Mind if I briefly join in this two man chat.
I was gonna say they looked like the KS series nathan horns (‘s’ standing for single) but I see you’ve done some interesting research to find your own answers.
Pete do you know if that guy who sold you the bells only deals with nathans or did he mention if he does any other horn companies (not that I need any more than what I have currently or on order)???
Those flat debris filters look pretty interesting too.