Its a little like comparing apples and pears i hate to say, as BSA did different levels of baffling whether it be a spitfire or anyother. I beleive the spitfire was less restrictive and probably more like the emgo. The T's and L's would have had more restrictive silencers but they would have met the MIRA testing needs and needed to have been quieter. (they probably also used them on spitfires for the test)
By some point in the 70's the noise regs got tougher and they started the first use of the megaphone silencer on the A65. prior to the OIF
BSA had three styles of mufflers. All three look the same on the exterior.
The Spitfire mufflers were straight thru inside with perforated tubing inside to hold the fiberglass packing in place. A broom handle can be pushed thru with no restriction. You can see thru with no restriction.
Another style was the interior with partial restriction. There were "V" shaped baffles alternating on each side of the interior partially blocking the flow of exhaust. A broom handle cannot be pushed thru. With a flashlight you can see thru with difficulty.
The other interior style muffler had baffles that on each side of the tubing that restricted flow even more. Cannot push a broom handle thru, and cannot see thru even with a flashlight.
At one time I tried to get photographs of the three interior styles, but the images never turned out usuable. Now with fiber optic cameras, like the what the doctor uses on me every three months, pushed up my nose and down my throat to the area near my voice box to check that the cancer they got rid of via chemo and radiation hasn't returned, interior images of the mufflers could be done. Probably a lot less uncomfortable process too.