I'm looking to buy a new bike in the next week or two and wanted to get some opinions on the license plate situation. My preference is obviously to be fully legal (or as close to legal as possible) but also want to make sure that I'm not getting ripped off.

Basically, the background is that I'm buying a used Honda Shadow from a guy (my Chinese mechanic) here in Beijing. The bike seems to be running quite well so no problems there. He's also selling a supposedly legit Jiangsu license plate, with green book and all, for an extra 4k RMB. At first this seemed like it could be a little high, but I was talking to one guy with experience in this stuff and he said if it's legit, that's a steal and he'd snatch it up if he could. I then also had a couple other guys come and take a look at the bike, one previous and one current honda shadow owner, to see what their opinions of the bike were. They thought the bike was good but the license plate was a rip-off. They were of the opinion that there was almost no way that a bike like that would have legitimate registration and it was almost definitely a copy of another registration of the same bike. They said I could get the same thing including the book and legit numbers that cops could look up for between 800 and 1500 RMB.

So basically, my question is, what's the best route to move forward? Is there anyway to verify beyond any reasonable doubt that the plate is completely legit, or is it better to just go with the cheaper option that will cover me in 90%+ situations and is likely pretty much the same as what the guy selling the bike is offering?

Thanks in advance for any help!