Greetings, All...

   Hmmm. Let's try this.

                        M.T.M.
                      5-26-24

For the loading gate pivot stud look here: https://www.cascity.com/forumhall/index.php?topic=55098.0

The ejection shroud cam looks to be the short one which means Italian parts.

There is no photo of the firing pin. The hammer has to be cocked to see it.

Your box is one of the early boxes that have the two haves hinged. That too can indicate an Italian parts gun. The later USA parts gun boxes had a separate lid from the box body with a cardboard sleeve that slipped over the entire box. 

I am thinking you have an Italian parts revolver, but it is an exceptionally nice revolver that you should be proud of, and hopefully an excellent shooter as well.

Hope these help, I'll admit to not knowing too many techy terms, so hopefully these are what your looking for. The hammer and firing pin pic's are already above.

As King pointed out, any standard .45 ACP load will be safe
IN A .45 ACP CYLINDER

In modern revolvers, it is the cylinder which is properly hardened to take the pressure.
For example, in the S&W 2nd model hand ejector, circa 1904 ish to 1917 ish
the original cylinders were made and proofed for the then standard ~12k to ~14k pressures of the
.45 Colt, .45 Webley, .45 blah blah blah

for the redesigned S&W Model 1917for the US military, the cylinders were heat treated to take
the .45 ACP loads and proofed as such in Europe.
from that timee forward ALL S&W ctylinders in the large frame .44 and .45 loadings were so hardened,
At a later time, S&W decided to harden smaller frame cylnders to approximately the same hardness.

Fun fact: When the FBI wanted a .357 ,  the S&W Model 10 heavy barrel was literally just reamed
for .357 magnums and sent to them. It later became the 3" .357 S&W heavy barrel Model 13.
Thus, the model 10 .38 spcl cylinders had ( or may still have) the same heat treating as the Model 13 .357
Saves a lot on different arts and possible mixups. (this tidbit from the archivists and histarians on the S&W forum)

yhs
prof m

Remove the cylinder and open the loading gate and take a photo where the loading gate stud fits into the frame so we can see if the hole is triangular or rectangular. Take a photo of the ejector shroud cam at the front of the ejector shroud where the ejector rod cams away from the barrel to see if it is the long or short cam. Take a photo of the firing pin to see if it is cone shaped or concave. The checkering on the hammer looks to be cast and not cut so based on that alone indicates an Italian hammer. Cylinders are sometimes a little difficult to tell unless you have a USA part to compare with, but I think the flutes are too pointed and not round enough.

The only person I know that could explain the serial number would be Gary Granger if he sees this thread.