From "A Pair of Wharfedales" page 200   ISBN  978-1-906715-14-4

                             Fs          Flux          Total Flux       Pe(RMS)    Weight    Diameter    Depth       BaffleOpening
                             Hz        Oersteds        Maxwells           Watts          Pounds       inches         inches               inches
W12/RS             45/50    14,000         156,000              15              12          12.375        5.25              10.875
W12/RS/PST     26/32    14,000         156,000              15              12          12.375        5.25              10.875

1 Maxwell = 1 Gauss/sq.cm. = 1 Line

1 Gauss = 1 Gilbert/cm. = 1 Line/sq.cm. = 1 Maxwell/sq.cm. = 10E0.4 Tesla

1 Tesla = 10,000 Gauss = 3937.25 Lines/sq.cm.

W12/RS manufactured 1961-1962  +/- 1 year
W12/RS/PST manufactured 1962-1965  +/- 1 year

Gang-Twanger     What's The Best-Sounding Wharfedale W90 Version?   Post #1
https://audiokarma.org/forums/index.php?threads/whats-the-best-sounding-wharfedale-w90-version.447484/#google_vignette

Hooke's law    https://en.wikipedia.org/wiki/Hooke%27s_law