There never was an 1851 brass frame. The closest was the Confederate Schneider & Glassick of which there are three known to exist, but only two have brass frames and I believe they were left in the white.
Sorry but no. The .44 Navies never existed either nor did any 44 on a brass frame. If yours is a .36 you can remove the cylinder scene and have an S&G tho. Pietta makes a lot of fantasy pieces.
Don't worry guy, it's all for fun anyway. Some like the brass, some don't. As the experts here say, just keeps the loads low and you're golden...err Brass.
Here's a little article about the things you asked.