Engine number question 230sl with factory replacement

[wwpepper]

Here is a picture of my engine tag and stamping.
I see there is a second tag below the first.
I learned from the Technical Manual that “Original Tauschaggregat” means “original exchange unit” in German.
The number stamped on the block matches my Data Card and the engine tag, but if you look closely the part of the pad where the last few digits were stamped appears to have been grinded down.
The second tag shows a part  number (Teil Nr) of 127 010 4100. I believe this is the general Mercedes part number for a replaced block or motor. There is another later 230sl that bears the same tag and number recently listed as sold on the internet.
After reading the Technical Manual I have reached the conclusion that  the dealer very early on replaced the motor or block and, accordingly,  applied the tag “Original Tauschaggregat”. The last few digits  of the new motor were restamped to conform with the data card and engine tag of the car getting the new motor. The original defective engine bearing the number 10-003217 would have been destroyed or junked. So that makes the engine now in my car the second but  only correct engine for this car, renumbered by Mercedes as such. As for the “aggregate number”, I have no idea what that means.
Does this sound like a reasonable assumption on my part?
The guy I bought the car from had it since 1997 and it was this way when he got it. It was reported to him at the time that it  was brought over to the US from South Africa.

[Cees Klumper]

My only note here is that, on some original replacement engines I have seen (including the one that is in my own car) the area where yours is stamped with the engine number, is 'blank' meaning the installing dealer did not stamp anything in. The fact that, on your engine, the area where the individual engine number is stamped, indeed appears to have been ground down at some point, suggests to me that this engine likely was installed in another car before yours. Making it a 'second-hand' engine and not likely the original, if we can even call it that, replacement engine.

As we can learn from this, it's very easy to make any engine appear to be the original one: just grind down neatly the area where the number is stamped in, then re-stamp the original number in with a correct die set (I happen to have such a set). Voila, 'matching numbers'.

[ja17]

I have seen these "Tauschaggregat" on engines, transmissions and differential many times over the years. I always assumed that it meant a factory reconditioned exchange unit was installed. Later cars had no separate tag on the engine for the engine number, just the stamped number or a blank with no number in case of a "new" replacement engine. 

[wwpepper]

A factory reconditioned exchange unit might make sense and explain why there were numbers to grind off.
I think it unlikely that in the 1990s,  when my seller acquired the car and  when these cars were not particularly valuable, that someone would go to all the trouble to acquire and install a second tag and then grind off and stamp new numbers.

But it does make sense to  think a new block or motor would be blank with no numbers stamped from the factory.

Maybe ja17 is correct and it was a factory reconditoned exchange unit. That would explain why it had numbers that needed ground off.

[Benz Dr.]

Which is why I say that matching numbers in our cars isn't worth paying any sort of premium.

[Pawel66]

There were many discussions on "Tauschaggregat" on this forum. Someone once wrote that engine replacements were not so uncommon those days and, if I remember correctly, some of the reason were the casting elements - too porous (if that is the right word).