That's a Semco muffler.

Dave,

The Semco system was somewhat popular around 1975, especially with R/C flyers.  It consisted of a set of adapters that fit over engine exhaust flanges, plus a set of mufflers of various shapes and sizes.  To install, you bolt the adapter to the muffler, then clamp that assembly onto the engine using a hose clamp style strap.  There were multiple size ranges, at least one for larger engines like .60s, and another for smaller engines like .15s.  It was not the lightest or most elegant system, but it did help get a few planes in the air.  It bridges a gap during the transition period when engine manufacturers had not yet retooled to accommodate the demand for muffled engines.

Peter

Dave,

The picture you linked shows a complete Semco system, including the muffler itself, the black adapter, and the strap.  The part number coding for the adapters includes both a color and a part number.  The Veco .19 adapter I linked above is in a pink package and marked 6-S, with S meaning small.  The adapter you sent is in a blue package and marked 4-L, meaning large. 

It's possible that some Semco mufflers may happen to fit directly, without an adapter, either by chance or by design, but the adapter system was the primary design thrust.

Peter

Air Misery,

A smuffler ain’t a smuffler ain’t a smuffler!

Here’s your pic of the Ex entry ole—attached.

The Semco already fits a Sooper Tigre Neptuno that I compared at 1.470 inches. I would just have to clean up the threads. Howsomesoever, it isn’t the same as the Sooper Tigre G21 holometry, which is much less spacier, being inside the stack. So one of them obtunium spacers that Peter was going on about would need to get involved. Which is good he brought it up, since I didn't know about them at all....

The OS Maximus .40 and .46LAs have 35.5 mildewmeter spacing, for blokes below the tropic of unicorn. Using M3x.5 pins.

No immediate plans for this Semco Goldy (don't say flash or the VAT kicks in), but liked to know what she’s good for…before I put it back into the storage box to wait for an airplane to prop it up on....

The Divot (with roos in the top paddock)

       Semco mufflers were made by Jim Semonian d.b.a. Braze-All Mfg. in Watertown, Massachusetts. As stated above, adaptors were used to fit the various engines. Jim and I were good friends and belonged to the same RC club. An ex-control liner, he always wondered why he couldn't penetrate the C/L community. I told him, but the reason didn't resonate until he spoke to a C/L group and was given the same answer; too heavy.

       However, I've found a use for them for C/L. My ancient Super Duper Ziltch needed nose weight, not to mention quieting the Fox 59. The Semco muffler took care of both. A plate was screwed to the muffler and a strap attached to the plate for mounting to the engine. On Spectra lines, the combo is a great flying Old Timer.

       I found the manifold in my 'box 'o' mufflers' and use it on my Twister as a tongue/diverter unit. No complaints about the dB's at Brodaks so it's a keeper. It's a butt fit on the Thunder Tiger 42.

       They're also handy for use on the test stand. Sadly, Jim's no longer with us.

       Ara