The Soviet ships usually changed onboard numbers of 1 times in five years, Last change of numbers was on May, 1st, 1990. After disintegration of the USSR numbers began to change seldom. In years of "cold war» at each exit on fighting service the Soviet ships changed onboard numbers on purpose to confuse the opponent.
For example: pass of passage Bosporus by the ships with numbers 801, 802 and 803 is ordered.
These numbers draw on boards of three ships, but one days prior to an exit on one of the ships – failure. Urgently it is put its number to the first ship and it direct on fighting service for 6 months …