This is what the AI AT bridge looks like, so I'm not entirely sure what you've got there... Clearly something aftermarket but it doesn't look right to me. Does it attach via the spigot?
Edit: Oh I see now... Kinda looks like someone adapted a KRG rail to an AI. One of these guys that knows more than I about these will be along shortly though.
Edit: Oh I see now... Kinda looks like someone adapted a KRG rail to an AI. One of these guys that knows more than I about these will be along shortly though.