I don't know either. However, I'd assume if you have OG on the RH side tank, you've got a good shot at still having at least the original tanks. How about the LH side tank - is it marked IH?
Also, there is the broadcast code/part number tag. As stated in the CRG article: All original radiators had metal tags clipped to the header plate of the radiator core, next to the passenger side end tank. The tags were painted at the same time as the radiator and thus should be gloss black. These tags identify the radiator via a large-font broadcast code - a two-letter code that was used by the assembly plant to identify parts on the assembly line. Also stamped on the bottom edge of the tag, in a smaller font, was the radiator part number. .
In your case, the tag would have UK with p/n 3010181under the UK.
When I did the front end mechanicals on my '69 RS, I replaced my original radiator with a service replacement. Historically, I haven't had the best luck with radiator shops and old radiators, so I went with the service replacement and hung the original on the wall in the garage. It (as well as the original heater core) is still a part of my original parts, just not in service any longer. If it hadn't been for the CRG report, I would not have known what it all meant. I believe that KurtS was the primary author. You might try asking/e-mailing Kurt directly.
Good luck with your research.
