This is a modern cast of an architectural element probably from the court of the Pyramid Temple at Khafre’s pyramid at Giza, which was subsequently re-used in the pyramid of Amenemhat I some 500 years later and was so deeply embedded in that structure that it can’t be removed.
The inscription on it is damaged in an interesting way – someone has carefully chiselled little lines around the outline of most of the hieroglyphs and motifs on the block. But not in such as way as to obscure them, everything is still legible.
The Met Museum’s website has quite a long discussion of the piece in its curatorial interpretation – they think the damage may indicate that it was reused more than once, perhaps originally by Khafre moving it from the building it was originally in.
The reuse by Amenemhat I was probably partly for pragmatic reasons (why quarry another huge piece of stone if you can just re-use an old one), but it also probably had more symbolism than that – it would link Amenemhat I and his tomb to the great old kings of the Old Kingdom.
This cast is in the Met Museum, acc. no. 1999.4.1 (see: https://www.metmuseum.org/art/collection/search/551054), and the original is still in Amenemhat I’s pyramid at Lisht.
See it on my photo site: https://photos.talesfromthetwolands.org/picture.php?/1371/category/6