PRODUCT CHANGED OR SERVICE TAG CHANGED

Hello all:

Recently, about 2 months ago, I had to check (query) a service tag status from a still operational server.   When I made this query at DELL.com  support section,  it reported me the correct server:

DELL PowerEdge SC1435  and the correct original configuration we bought from DELL

Today, due some external circumstances, I needed to check this same service tag again, on the same support pages, and it turns that I am getting a totally different equipment:

DELL PowerEdge 1950 and a different configuration, of course.

Why or how on earth the same service tag was ONCE assigned to one very specific (and physical product which I have in my possesion, as well as its purchase inoice from Dell),  and now,  it is assigned to a totally different product. ?   How could this happen?

Is it possible to track and get the history of a SERVICE TAG, from the time it was FIRST assigned to a specific unit of a product  ?   And,  the re-assignments it  has suffered across time (hopefully this does not happen) ?

In fact due to an incident, we are claiming the reposition of that machine, the one with the original service tag.  Now, it turns  the query returns a different model of equipment (and configuration) and thus, there are problems with discrepacies, as you probably can guess.

Any comments are more than welcome,   thanks in advance.

Felipe