Hi Ulli, Look through the fins. 4CX1000A fins are internally flat. 4CX1500B fins have small convolutions in each fin. 73 & Good morning, Marv WC6W -- "Ulli Grunow" wrote: Hi there, Can someone tell me, how to distinguish visually a 4CX1000A from a 4CX1500B from outside ?!? There is no printed label anymore visible. The tube in question is used and comes from a marine equipment manufacturer DEBEC (Germany) Is there any difference, so that looking on the tube we can definitely say that it is a 4CX1000A or 4CX1500B ?! Is there a sinple electrical test probably so we can find out ? Please let me know. Thanks for info. Ulli, ON5KQ _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps ___________________________________________________________________ Try Juno Platinum for Free! Then, only $9.95/month! Unlimited Internet Access with 250MB of Email Storage. Visit http://www.juno.com/value to sign up today!