A warm Welcome to you ecrotts21, and the handsome Smith & Wesson which you have inherited. The K frame M&P model has been an icon for over 120 years, and deservedly so. If you have any questions about the mechanism or its operation, you might check with a local gunsmith if you have one to consult.
By 1919, the M&P cylinders were heat treated for greater strength and durability. So, your revolver is quite capable of digesting all standard modern 38 Special ammunition that you might care to find and use in that revolver. Some believe, myself included, that jacketed ammo is a bit harder on the barrel, and that lead bullet varieties are easier for it to digest. Of course, seeking accuracy and a great deal of fun, using all proper safety protocols.
In case you have not heard of it, the Standard Catalog of Smith and Wesson, 4th edition, (SCSW 4th) is a notable book that will give you much overall history of the many Smith & Wesson models over the years, including that handsome nickel plated piece now residing with you.
All best to you.