Hello Marcus,
Since "pic 0" shows several 2-digit serial numbers of some parts, most likely this was a military gun that had some small parts refinished and got rebarreled as well. The side plate, a replacement piece, should have the 2-digit serial number stamping as well.
The commercial-style serial numbering had the 2-digits "hidden" and mostly stamped on edges of the parts.
"Pic 02" appears to show the extractor as being strawed...but I am not 100% sure. It should be blued.
"pic 04" appears to show that the front portion of the frame where the serial numbers are stamped may have been refinished. The middle two numbers are very faint; possibly the depth of original stamping was lost due to polishing of metal and the outer two numbers may have been re-struck...?
Regards,
Pete... <img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />