I'm not 100 % certain but would bet long green that the 24's were all furnace brazed.It's relatively easy to tell. Take a sharp scribe and scrape the alloy in an inconspicuous place like the side rib under the forearm. Study the exposed alloy under magnification, if your eyes are as old as mine. If the ribs are soft soldered, the alloy is silver. If the alloy is bronze it will be bronze coloured.