Mumbai, Dec. 31 -- COMEX Silver futures tumbled today as selling pressure stayed in place on last session of the year after prices hit a series of record highs recently. COMEX Silver futures are trading at $70 per ounce, down 9% on the day, giving up a 10% spike in last session. The metal is still up around 140% this year but there are signs of some moderation in demand from funds. Precious metals speculators sharply cut their net long positions in the Silver futures markets last week, according to the latest Commitment of Traders (COT) data released by the Commodity Futures Trading Commission (CFTC). The non-commercial futures contracts of Silver futures, traded by large speculators, hedge funds and retailers, totaled a net position of 363...