Mercedes Benz Radios 1968-1971 For the #00 SEL 6.3
You will be able to tell the correct radio for your car by checking the options plate near the radiator. It's possible that this is the correct radio originally supplied with your car if your car was originally supplied for the U.S. market. The radio in the auction provides only for the "M" (AM) and "U" (FM) bands.
In the case of my '69 6.3, the options plate shows that a radio was supplied which is visually similar to the radio in your auction. However, my radio was the Becker Grand Prix "LMKU" radio. It looks like the one in your auction except the dial is bigger and it provides for the "K[urz]" (shortwave) and "L[ang]" (longwave) broadcasts.
I don't know much at all about these radios, and will be asking advice soon, I'm sure, about how the buttons and search functions work.
There are any number of Becker radio models that look so much like the one that came in your car, I don't think many people would notice the difference. You can even get Becker radios that look like they absolutely belong in your car, but they're stereo and include a cassette player!
You were wondering, I think, about the auction seller "email@example.com". It's not evident from the way the auction's worded, but this is a business, not an individual. I have corresponded with individuals named Aaron, Arend and Roger, all at this address and all evidently with some experience with older Mercedes.
I bought my radio from them. They swear that it worked when it was removed from one of their personal vehicles (Roger's) and that it should work now. I have _not_ installed the radio yet, so I can not testify to that. They forgot to ship the chrome surround with my radio, and they say it's on the way now.
Mike Trei is the one living God of this, so he can provide the definitive answer. But typically the earlier 6.3s (1968 through 71s) had a Becker Grand Prix with Wonderbar (self-seek) and Shortwave / Longwave /AM/FM capability as a specified option; the standard radios were generally the stock AM/FM non-Wonderbar Europa with either four AM (BC) and 2 FM or four FM and 2 AM (BC) presets..
Having had a stock Europa in my 69 6.3, I replaced it with a Becker Mexico Cassette (second version from the late 70s) which looks similar to the regular Beckers, as mentioned, but with a cassette slot at the bottom and no preset buttons. I believe the latest 1971 and many 1972 6.3s came with the Mexico Cassette as a specified option. This Radio cost almost $2000!!!
Also, most if not all US-spec 6.9s came with the Mexico Cassette standard. The radio looks in character with those cars as well, proving the classic timelessness of the Becker designs. (I replaced my 6.9s radio with a Becker 754, which is a more modern-looking 1986-87 AM-FM-cassette unit with a digital LCD display.
firstname.lastname@example.org is a reputable & longtime eBay and regular-mail vendor that specializes in vintage Benz parts & memorabilia. They are honest and easy to do business with. Anyway, a US '68 would most likely have been delivered with a four band mono Grand Prix with five presets LW BC SW FM FM. Some had a mono Europa with similar presets. What radio you decide to put in depends mostly on which speakers are fitted in the car. If you only have the top center dash speaker and perhaps a center rear speaker, you will want to use a mono radio. If you have stereo speakers fitted in the kick panels and perhaps the rear deck, you should fit a stereo Grand Prix, or Europa. You could also fit a stereo Mexico cassette although technically it wasn't available until '69. Four band stereo Grand Prix are very hard to find. Please note that many European models from this era, mostly four banders, only go to 104 on the FM dial. You can also fit an Olympia glove box cassette player or a Reims shortwave adaptor if you want to add these features to a radio without them. I'm a big shortwave fan and love the Reims option.
I would be a little wary of buying radios on eBay without some kind or warranty or return priviledge. The seek mechanisms on Grand Prix and Mexicos are frequently faulty, and the band change switches are often corroded making it difficult to get good AM. If you believe Roger's stories of having pulled various radios from his cars, he's owned one hell of a fleet over the years. Buying a rebuilt radio directly from Becker might be pricy, but guarantees a perfect working unit.
Here's a few more current eBay auctions to look at;
#406579327 Mono AM FM Europa with six buttons. Nice, but the correct radio for a '68 6.3 would have the AM buttons marked BC, and only five buttons.
#408078649 Stereo Mexico cassette. Looks good, technically a Mexico for a 6.3 would have a different seek bar that reads Becker Mexico Stereo.
#410132964 Mono five button Europa Am FM. Looks good apart from the AM buttons instead of BC.