Mikuni Carb ID Help Please

[OzzyElsie]

This was among a job lot I got and I was thinking of using them on the RZ350 motor I have. I think their general description is TM28mm but there appears slight differences between the two carbs. I don't think they are RG250 although very close - they each have a choke plunger whereas the RG had the one and connected with a tube IIRC.

Next to the choke one has a vent (for what purpose) the other doesn't. The choke plugers look wrong as well.

They may be off an MXer of the period.

Does any one know what that little brass connector is for in the last photo?

(Left click on photos for larger image, and click again in Photoimage to get even larger image.)

[hybrid]

They could possibly be RGV, but one of them would normally be a different angle.
Unless they weren't actually a pair, but one carb from two different bikes.
I can't remember what the chokes were like on RGV though.

Also, if you use "hotlink to forum" on postimage instead of "thumbnail" the images will display bigger.