The coinsearch coil were used on the first 2 Sovereign, the original and the XS so they are coils made back in the 90s and where changed to the BBS in around 1998 when the the XS2 came out. Many of us love this coil and a I find that for someone new to the Sovereign it makes the learning curve easier as it seems to drag out the signals more so they are easier to hear. The only problem were these are not waterproof like the BBS coils are. I find the coinsearch glided over the ground much better as it is a closed coil, found my deepest coins with my 8 inch coinsearch in a very old well worked park with my XS2 and I had cut the cable down on this coil and felt it was a more sensitive for me anyway. I got these deep coins by knowing my Sovereign well and going slow.
Now when these were more common and lot of them around a used 8 inch Coinsearch sold around $60-$75 in good shape and new ones sold for around $100-$125, now that there is less of them around as some like me keep one around as we know what they can do. I have seen some advertised on the auction site that were trying to get $140 for one that were like new, but don't remember if it sold or not. At this time a feel a nice used 8 inch coinsearch coil that look and works good would be worth $100 and those that don't look as well, but work great will be around $75.
That's my opinion anyway.
Rick