A computer implemented system is provided for exchanging shares in an exchange traded product. The function may be a fixed predetermined ratio or it may vary depending upon the level of turning force or torque supplied by the manual input drive. The implantable biomarker is preferably mounted upon a surgical instrument or surgical implant and used in conjunction with an image-guided system to enable a surgeon to quickly and easily find the location without requiring extensive x-rays or the use of expensive and cumbersome equipment. 3% of niobium, less than 2000 ppm of tin, less than 2000 ppm of oxygen, less than 100 ppm of carbon, from 5 to 35 ppm of sulphur and from 0.