[BEAGLEBREWINGCO]

I figured out how to view the pictures. 

Does that thing fit around the dip tube (dip tube goes through it) or does it sit on top of the dip tube?

From your first picture, it almost looks like the keg has female threads, is that the case?  Can you post a picture of the keg post?  Is there a manufacturer's stamp on the keg?

Thanks to all for assistance in putting pics up - I forgot also to answer the Q - yes, the dip tube fits through the 'washer' so the washer sits around the head of the dip tube. So the washer surrounds the flare of the top of the dip tube.

[narcout]

Yes the keg has female threads.

I've never seen that before, interesting.

I forgot also to answer the Q - yes, the dip tube fits through the 'washer' so the washer sits around the head of the dip tube. So the washer surrounds the flare of the top of the dip tube.

One of my 10 gallon corny kegs (a very old one) has something similar, but I don't know where you can find a replacement.

It might be worth a call to these guys, as they carry some older keg parts (race track lids, etc.): http://www.chicompany.net/

Otherwise, maybe take it to Home Depot and see if they have something similar.  Per the link I posted earlier, a rubber slip joint washer might work with a bit of sanding.

[BEAGLEBREWINGCO]

Yes the keg has female threads.

I've never seen that before, interesting.

I forgot also to answer the Q - yes, the dip tube fits through the 'washer' so the washer sits around the head of the dip tube. So the washer surrounds the flare of the top of the dip tube.

One of my 10 gallon corny kegs (a very old one) has something similar, but I don't know where you can find a replacement.

It might be worth a call to these guys, as they carry some older keg parts (race track lids, etc.): http://www.chicompany.net/

Otherwise, maybe take it to Home Depot and see if they have something similar.  Per the link I posted earlier, a rubber slip joint washer might work with a bit of sanding.

Thanks for your comments folks - I might try those slip joint washers and a visit to my local hardware store. Just FYI - I'm located in Australia and I think these kegs are old lemonade kegs - I can see a faded soda brand label on one and some initials which would correspond to Cadbury Schweppes Australia which would at least explain their history. I'm sure with a bit of effort I will be able to get some o-ring / washers that work - I will have to keep experimenting - thanks for your help !!