There was a matching serial number on my latch/sight too---and it came close to going away---thanks to a REALLY bone-head move!!
The gun was ALL apart from its welcome bath---and going back together. Some knot-head who shall remain nameless to protect the guilty, put the latch in place---and closed the barrel---the latch only----no sight carrier (!!!)
We digress at this point to discuss some aspects of these things nobody in their right mind bothers with. The other folks, those from the lunatic fringe, think they're interesting---if not important.
The original S&W latch/target sight assembly started life as a plain, everyday latch. After not much head scratching, an inventive soul milled a slot in it from one end to the other---and milled a notch at the back end (to hold the sight carrier). Now this slot SEVERELY weakened the tang which runs forward, and bears against the barrel catch cam----which bears against a STOUT little spring-----STOUT!! As scary as this might sound at this point, it's of no moment, because the sight carrier has its own tang which fits quite nicely in the slot----and makes everything strong again.
When the barrel was closed, the latch tangs (two where there used to be one, and where there should now be three) made contact with the barrel catch cam (AND its STOUT little spring), and were unable to cope with the load. So they bent. They didn't bend very much before they went SNAP!! They went SNAP because the steel they're made from is steel in name only---same as the rest of the gun.
All this was followed by a series of bad words----followed by "Now what?!!"
"Now what?!!" was followed by a search for a WIZARD gunsmith---ending with Chris Hirsch, who said, "I know I can fix it.". This was preceded by a host of others who said, "I don't know if I can fix it or not---but I'd sure like to try."
The next step was to create a fall-back position---just in case. George Dye to the rescue! He came up with a latch/sight assembly that looked like it had come from S&W's Parts Department---Praise be to Allah!!
Off goes the barrel and busted latch to Sugar Land, Texas. Back it comes in a matter of days-----fixed! It was not only fixed, you can't even tell where it was fixed---even if I showed you where to look!
Like I said---a WIZARD gunsmith!!
Ralph Tremaine