Hello - that's a Martin Symphony ( or New Symphony ) model listed on Jim Donaldson's Dallas Gearhead Martin Committee page about 1/3 the way down the page:
Martin Committee
I've seen collars or patches done to encompass the bad area as long as good seal is made. It's nearly impossible to patch it back using silver solder -- there's nothing solid to solder to so a collar is used. Getting an replacement leadpipe from M&K Drawing might be possible with the proper measurements or finding a junker horn with a similar leadpipe might work but you gotta like these horns to make it worth your while as others have said.
Or, as Robt suggested -- you might be well to sell it off -- how much you want?? Did I mention I love these old Martin horns? I have almost 1 of every model known to have been made from the early 1900s.