Latin Grammar - "Optimus Princeps" vs. "Optimo principi"

[Paddy]

A question about Latin grammar.

The title "Optimus Princeps" was awarded to Trajan. I assume this is the nominative case. However, on his coins the wording is "Optimo Principi".

Question:

* Is "Optimo Principi" the dative case?

[curtislclay]

Yes, dative case, because the Senate and the Roman People (SPQR) are dedicating the coin in question, or expressing their best wishes, TO their "Best Emperor".

Trajan's whole obverse legend is in the dative case for the same reason: all dependent on that SPQR acting as subject.

[Paddy]

Yes, dative case, because the Senate and the Roman People (SPQR) age dedicating the coin in question, or expressing their best wishes, TO their "Best Emperor".

Ok thats what I thought, but wasnt sure. What confuses me now is the fact that they put that legend on silver, when the silver minting was controlled by the emperor, and base coins were minted by the senate. Makes more sense to put that legend on coins controlled by an entity other than himself.

Anyhow, here's another grammar question. What is the difference grammatically between "populus" and "populusque"?

[benito]

Populusque
The " que " means and. 
Senatus populusque .......    The Senate and people.........

[Paddy]

Populusque
The " que " means and. 
Senatus populusque .......    The Senate and people.........

Thank you both for your replies!