Makers marks for the M1809 Prussian musket will be Saar, Potsdam, Suhl, Neisse and possibly others that I can't remember right at the moment. The Prussian musket, imported early in the War by the North only was considered an arm of the 4th Class. While a sturdy and well made musket and utterly flawless in function, it was considered too heavy and took non-standard ammunition - .71 caliber as opposed to the US standard .69 caliber. The US standard ball for the .69 smoothbore musket was both .64 and .65 in diameter, the Prussian used a .67 and this was simply not available, making the Prussian muskets unacceptably inaccurate with the US ball. It's biggest problem, though, was that maintenance was very difficult - no spare parts were imported and from that standpoint, they gave Federal maintenance armorers huge headaches. As far as Confederate use? The South early on got huge contracts for British and then Austrian arms and did not import many from other sources. Captured Prussian muskets may have seen some Southern use but mainly would have gone to rear echelon troops that saw little if any front line service. Like the North, the average Southern soldier was well armed by mid-1862 and 4th Class arms were simply put into storage or disposed of.
As stated earlier, the Prussian muskets came here early and were issued and used early by US forces who were desperately short of arms, especially in the Western Theater, but by late 1862, better weapons were available and the Prussians went into storage to be surplussed quickly after the War.