Whites BlueMax coils will only work with Whites metal detectors that operate at 6.59 khz made from 1989 to present. The only BlueMax coil Whites made that would fit other brands was the BlueMax 256 coil. 10" and stamped with a '6B' on the mounting ear. Made from 1988-1989.
Whites did something to their coils(1989) that didn't allow for use with other brands...namely Teknetics and Bounty Hunter units. Whites and Tek/BH shared the same frequency back in the mid to late 1980s. 6.59 khz.
There was a coil cord adaptor that enabled both brands to switch perspective coils. I have one of the Tek/BH to Whites coil cord adaptors. Tek/BH could use the Whites coils marked with '6B' stamped on the mounting ear.
Keith Wills made a special cord adaptor that will enable me to use Tek/BH coils on my Whites 4900/SP3.
In answer to your question...NONE. Shown is the Tek/BH to Whites coil cord adaptor. Not for sale as I only have one left.
WORD UP! I speak my mind when it comes to the older metal detectors.