A quick browse of the archives serves as a great reminder that this isn't an "ordinary Suzuki RG500", it's a full on factory racebike, the RGB500. This example has a rather thin description but like many bikes on eBay it could be listed to see what interest may be out there and further investigation will be required. For instance the ad states that it may have raced in the Isle of Man TT but can't yet prove that. Nonetheless, these opportunities don't come up that often.
from the seller:
This very rare motorcycle was purchased by us here in the US, we were told it was raced at Isle Of Man, but we are unsure of the team it was raced for. Great vintage shape as you can tell from the pictures. This motorcycle has been on display for many years and has not been ridden/started during that time. This is the same kind of motorcycle that piloted Barry Sheen to many GP wins!