Very possibly a Austrian Lorenz. Leander Stillwell of the 61st Illinois is recorded as having a .54 caliber Lorenz. The Lorenz came in both .54 caliber (Austrian Army issue) and .58 caliber (made under contract for the U.S. Federal government, with the contract taken over by the Confederacy in 1863).

As to the .69 caliber bullets, they could be from the Austrian Model 1842 (originally made with the Augustin type lock, aka console lock). Many thousands of these were issued in the Western Theatre on the Union side early in the war. On the Union side in the Western Theatre, I think these were much more common than the Lorenz. The Model 1842 was .69 caliber if a musket, and .72 caliber if a rifled-musket. These were common on the Confederate side later in the war (1863 and later) in the Western Theatre.

I know very little about the "real" Prussian muskets. However, John Spangler says that the Model 1809's were widely used by Yankee units, but they were .72 caliber. Some of the State units of Iowa and Ohio are known to have had these, for instance the Fourth Iowa had them. I have seen Model 1809 with Ohio stamped on them. I see alot of bullets for sale that are marketed as .69 caliber Prussian but I do not know what Prussian gun those would be for (or if the sellers just have them mis-identified), ...perhaps Edward's book has the answer to that question.

In addition the Model 1842 Springfield musket saw a lot of use during the Civil War, and it was .69 caliber. 172,000 of these were made from 1842-1855. I don't know how common (or uncommon) these were in the Western Theatre.