Two more bull/prow aes grave semisses have come to light at Praeneste in archaeological contexts and are now on display in the museum. This is HN Italy 359 = Vecchi 276 = Haberlin, pp. 157-158 (specimen in trade, second specimen in trade). Thomsen ERC III: 149-150 thought these might be Roman aes grave but this has not been accepted by others. Vecchi notes a weight range of 167.96-118.20g.
Previous finds were Praeneste prior to 1893 and the Ariccia 1848 hoard (c. 28 km SW of Praeneste, ~6 hour walk due to elevation changes).
Now with THREE pieces found at Praeneste, I think we should assume that it the place of manufacture until further evidence comes to light.
The other major thing to note is the regular use of aes rude in Funerary Contexts. This was already observed in the 1907 excavations (see AJA 1908 summary below), but is now reconfirmed by the 2007 finds.
It seems that these aes grave may also be from funerary contexts as they were unearthed in the same Colombella excavations. – private correspondence with the excavator suggests the aes grave was NOT from a burial context.