Welcome to the forum. As stated pics would help. Also if look at signature lines or sayings (many have them) will appear below the "Like" button. There is a very faint line there and are not a part of the actual message.
welcome01 to the forums from the Wiregrass! S&W didn't make many Model 28's in nickel. I think the count is around 70 with most of those going to the FHP as 5" guns. So, your gun may not be a Model 28, especially if you think it is pre-war. Could be a pre-war .38-44 Heavy Duty that has been reamed for .357 which many were. Pictures of the gun will help us get the approximate manufacturing period and model more correct. And, you may be absolutely correct, but we would feel more comfortable giving advice on something we had actually seen.
Pre-war serials for .38-44 HD's were 5 digit with no letters. I believe Model 28's all had 6 digit serials prefixed with an S up to 1969, then prefixed with an N. I've never seen S&W use an X for the serial, but never say never with S&W. Someone could have overstamped the original letter...or added it to an existing serial. Early guns will have the serial stamped inside the ejector dock and on the back of the right grip panel as well as on the butt. These extra stamps were eliminated around 1958.
We'd like to help you solve your mystery. I hope the above helps you help us.