the print in the ad:
"Introducing the new MXL 604 dual capsule Instrument Miking System. Based upon the highly accepted MXL 603 microphone, The MXL 604 is the latest in quality instrument microphones. The 604 delivers the dynamic range required in the most demanding instrument miking applications. It features; -10dB switchable attenuation; selectable low-frequency roll-off; and an interchangeable omni-directional capsule making the (the) 604 perfect for acoustic guitar, ambient and overhead drum miking. Audition a new MXL 604 today and see how MXL has again moved the bar in affordable microphone technology."
aside from the typical b.s. towards the end, it looks like marshall has added a roll-off, pad, and omni capsule while keeping the price the same at $100. seems like a good deal. i wonder if they kept the innards the same or is it just "based."