Howdy
the serial number engraving helps but it doesn't mean that someone couldn't do that on their own. The barrel also should be marked. The slide/extractor cut is the clincher. All the sub-caliber guns had this to lighten the slide and help things work. The front site is something new, never seen a stake on front site before. the hammer could be something that somebody dreamed up. Just from your description I would say that you have an original that has seen some work. If you want to send some pictures feel free. I just got another 38super and it shoots like the glory-of-God! This is the second one that I have had and I won't sell it this time!
Hope this helps1
L8r
Conley