Serial #’s A 04410 and A 04661. The Acoustic Research AR-10 Pi is designed to reproduce music in the home as accurately as the state of the art permits. It’s ability in this respect represents a number of significant evolutionary improvements over previous designs. Further, the AR-10 is intended to offer an unprecedented degree of flexibility without sacrifice in accuracy. The combination of these characteristics, we believe, represents a significant step forward in loudspeaker design. Type: 3 way, 3 driver loudspeaker system. Recommended Amplifier: 25 to 150W. Crossover Frequency: 525, 5000Hz. Bass: 1 x 305mm acoustic suspension. Midrange: 1 x 38mm hemispherical dome. Tweeter: 1 x 19mm hemispherical dome. Dimensions: 354 x 635 x 273mm. I had the Woofers Reconed five years ago by an incredible Speaker repair guy and had some custom covers made for the front. The originals were foam and they just deteriorated. These speakers are in excellent condition. The tweeter dust caps do have dimples but that does not affect performance at all. The sound quality of these speakers is amazing! I’m approximately 4 1/2 hours from LA and 1.5 hours from Las Vegas and I go to both places often.