@refusedname - Will have to scout "reputable shops," nationwide, for sure.  I'm all ears to any that you suggest.  I'm going to research this Igor fella mentioned below.  Judging by the current bid, it seems highly unlikely the reserve will be met, which is fine.  A lot of major life events have crept up (it took more than a few months for this latest work to be done by the dealership, as they had to wait for parts), some involving a scalpel, which compels me to scale down.  I've even been too busy to get to the dealership to figure out what in holy hades happened to the Carat that was supposed to be cleaned.  Saying I'm disappointed is an understatement.  However, it's not the end of the world.  

On the bright side,  I've been profoundly changed by the last Top Gear episode about "Restomod Mercedes."  Within the last 10 years, 3 shops that service Mercedes have closed in my area (two of them involving an octogenarian German MB Tech who had incredibly fair and reasonable prices) and it actually took two years and new management for me to finally get this W126 serviced at the only place left, this particular dealership. In retrospect, I should shipped it out of state to my MB Tech buddy who sold it to me, as this was a very expensive gamble gone terribly wrong, lol. Alas, I'll survive selling my kidney to pay for it, lol. 

Seriously, this lesson points to that Top Gear future.  Thus, restomodding these older Mercedes (I have an '01 S55 AMG that I had planned to use for a similar W108 featured in the Top Gear episode) appears to be the way to go and restomodding, judging by the latest auctions, doesn't appear to adversely effect the sums fetched by those parting with their "resto-modernized" vehicles.

@refusedname While I believe your 50k estimate on this collector grade vehicle is wildly excessive, I do believe that you're pretty close on the $100-$125 going rate in this present market.

@AMG5pt4 This Carat needs neither engine nor transmission work, as a service was performed on both the engine and the transmission by Mercedes of St. Clair Shores, in 1/23, where the Carat is presently located.  May see if I can have some videos uploaded on Monday attesting to its running and whether the dealership detailed it as I had thought they were going to do.

@SwissBliss I own 6 other Mercedes and I've owned several others (including a Jag).  The leather in this Carat is ridiculously opulent.  I have not researched this type of leather, but I didn't want to even put any kind of leather cleaning solvent to clean it (I have all of the literature surrounding the build so I'm sure it specifies what it is).  I just spoke to the Service Advisor about what looks like a stain on the carpet behind the driver's seat and I asked the photographer what in the world was that?  The Service Advisor says he'll speak to the Tech who serviced it and a couple of photogs have gone in and out in order to get certain shots like of the Cartier time piece and the VHS built into the center rear seat.  I asked the Service Advisor about possibly detailing the interior, but - once again - as someone who owns several Mercedes, this Carat is a completely different.  It's a singularly unique, custom designed luxury carriage and I wouldn't just want anyone doing the cleaning.  I think that Jay Leno might have done one of his episodes on a Duchatelet Cullinan build. These are pretty special vehicles and they do not come to market too often. Thus, this is a piece that a serious collector might add to their collection, knowing in advance, as you've mentioned, that interior restoration will not be cheap.  Last I checked, we do not acquire these cars because they're cheap. 

As I've mentioned, both the engine and trans have just been serviced and the Carat runs excellent.  However, unless a serious collector arises, I could see myself restomodding/modernizing the drivetrain with a supercharged M1113, as the intrepid, brilliant Matt Kweik - on one of the latest Top Gear episodes - has done.  In fact, I have a fairly pristine W108 ('67 250SE) AND an '01 S55 AMG and Matt has inspired me to similarly restomod my W108 (which I could have done to the Carat)!  Matt will force many Mercedes collectors to rethink our purist views to collecting because his value-added approach is actually booming here and in Europe where I hear that such restomod, bespoke vehicles in the UK reportedly retail for 150k and up.    

@SwissBliss Thank you for your constructive comment.  If the reserve isn't met, I will undoubtedly shell out the bucks and have it restored, but perhaps also restomod the drivetrain (Note: this one cost a staggering sum to simply service) the way the fine gentleman on Top Gear has done both his W108 and W123 (two other classics - one a movie car - that are models that I similarly own and will also be selling).  I will be making my way to the dealership to assess matters, tomorrow, as the lighting in the pix on the rear driver's seat floor appears to indeed make that look unclean when I as a single individual has never sat back there nor have I ever seen that looking like that.  So, yes, this rare W126 indeed has a deliberately left untouched "patina" (read: worn seats amongst other weathered features) earned by the previous owner and the leather seat appears to need that unique leather reupholstered or restored.  As I've said below, I would rather have someone serious about restoring it, purchase the vehicle.  However, thank you for providing that reference!    

@Rivolta This Carat has zero leaks and no rust, as, unfortunately, this vehicle never received any duties as it was meant to squire around nonagenarians, which sadly never happened. It was a garage queen for the entirety of my 13 years of ownership.  Frankly, my caregiving responsibilities had been such that I will be essentially "new car prepping" the Carat.  To my knowledge, the only feature - aside from the missing curtains - that the master MB Tech seller informed me that he never activated was the center console refrigerator.

@silkyatl    Within my ownership tenure, this vehicle has been free of any accidents as it has stayed garaged and rarely driven as intended.  This is 1 of only 16 bespoke Cullinan "Personal Limousines" as Duchatelet refers to them, that they have curated in 1986.  Being that this vehicle spent it's entire operating life in Sunny South Florida (I've driven it less than 10 times and, unfortunately, never for leisure), someone interested in restoring the interior - I have decided - will have to handle the wood veneer pieces that the Florida Sun has mercilessly "Caressed," if you will.  Due to the rising value of these soon-to-be, perhaps, rare museum pieces (for some - please consult the latest projections of the rising value of the W126 in places such as Hemmings, Hagerty, the Robb Report and even Hot Cars), I have decided to let an expert perfectionist of considerable means handle the professional restoration of this rare Mercedes.  Finally, I will consult with both the photographer as well as the dealership where it's presently located as to whether it is the lighting or whether it was properly detailed as the king's ransom that I am paying assured would be the case.  Last I checked, all of the windows worked, as well as the heat and AC.  The freshly performed services assures that there are no leaks, oil, exhaust nor otherwise.  However, I will reaffirm everything with underside pictures that I will add to the gallery.  Thanks for your interest!

@Rivolta I will provide pictures of the undercarriage Monday or Tuesday evening.  I will see if I can do an assessment of all that you have asked in that timeframe.  Thank you for your bid and interest!