Although i dont own or use a Tejon i do use a similar machine that is been modified from new from Pentechnics,this is based on the Vaquero but modified more for the UK,my machine is called a 'Laser Trident11 Extreme' which is based on the Vaquero,but runs @18.5khz if i recall,alot of our small hammered silver coinage including cut halves and quarters run into the foil range,the silver content can vary by a fair amount depending on how much silver was available i guess at the time,so with so many variables its alot harder than a set standard silver content.If we eliminate foil we will also eliminate these desirable targets as well.
The Trident11 Extreme also has the high tone modification and also other mods as well,but of course these are not disclosed as its the companies secret i guess and they want too protect these,but mine has the Tejon battery box at the top of the stem behind the armcup rather than the single 9v battery in the normal position.I think its a lot sharper in its response especially on small targets,but i must admit i am not a fan on the 11x8 coil that comes with the machine,i currently use the NEL Snake 6.5x3.5'' which i find is a deadly combination on trashy roman/saxon sites which can be littered with general nail and everyday trash that has accumulated over the 1000s of years.