This graphic below shows the alleged Spandau toggle link in comparison with both Erfurt toggles and illustrations of two types of Spandau toggle link examples from Gerard Henrotin's e-book "The Luger Producers"...(highly recommended by me for Luger reading)
Notice that the link in question has a serial number stamp that more closely resembles the serial number placement used on an Erfurt Toggle, and that there are other Spandau example marks that are no where to be seen.
There also appears to be present what looks to me like a crown/N in a place where there would not normally be on one of the Spandau links (that were used for the illustrations in Henrotin's e-book.
FWIW, IMNSHO, I believe that this was an Erfurt toggle link that has been welded, ground and
engraved with the letters for Spandau. This would account for the stamp being white instead of the same color and consistency of the crown and serial number digits. There are also inconsistent polishing marks present(as shown in the photo of the link on auction). Vertical marks over the crown/N and horizontal marks over the SPANDAU... A little amateurish looking to me... not something I would expect to come out of a German government arsenal.
anyway...that is my $0.02