That explains! The fourth flag also looks like a 6, a fifth flag being obscured by the structure. Thanks!

Found this picture of Perekop arriving in Havana, Cuba three years ago. The call sign then seem to be RFHJ, trying to read the signal flags to the port side

RBEX 994 18 4 1450 994 = SML FOR RJH82 RCD88 RMB97 = 04121 99572 10202 41/98 82708 10158 40181 58002 70313 88220 22200 00150 20203 04013 = + RBEX K

RMLV 816 15 1 0901 816 = FOR RJZ4 = 01061 99649 10391 41498 43405 10090 40330 52030 70200 86421 22200 00090 2/// 01013 = AR RMLV K

Unknown Russian Navy Vessel, RMLV, sent a weather report on 4576.5 kHz CW 01OCT2026 at 0613 UTC to Russian Navy Northern Fleet Naval Base in Severodvinsk, RJD99 RMLV hove to at position 64.9N 39.1E RJD99 answered on 6387.5 kHz

After the weather report RJD99 asked RMLV to establish a USB link with RJD99 transmitting on 5964.5 kHz and RMLV on 6006 kHz: RJD99 QSU1 QSX 6006 QWH 5964AAA5 K

RMLV 917 15 29 2103 917 = FOR RJZ4 = 29181 99648 10393 41398 41807 10110 402_0 57030 70200 86421 22200 00090 2//// 29013 = AR RMLV K

Unknown Russian Navy Vessel, RMLV, sent a weather report on 4576.5 kHz CW 29SEP2026 at 1821 UTC to Russian Navy Northern Fleet Naval Base in Severodvinsk, RJD99 RMLV hove to at position 64.8N 39.3E RJD99 answered on 6387.5 kHz

RCIM 235 17 29 1200 235 = FOR RJZ4 RIF4 = 29091 99678 10408 41498 62112 10098 40192 58018 70122 86117 22271 00096 20202 88000 29014 = AR RCIM K

Unknown Russian Navy Vessel, RCIM, sent a weather report on 4619.5 kHz CW 29SEP2026 at 0938 UTC to Russian Navy Northern Fleet Naval Base in Severodvinsk, RJD99 RCIM at position 67.8N 40.8E heading North West at 1-5 knots RJD99 answered on 6259.5 kHz

RMLV 531 15 28 2101 531 = FOR RJZ4 = 28181 99649 10385 41498 43104 10130 40290 52020 70200 86421 22272 00090 2//// 28013 = AR RMLV K

Unknown Russian Navy Vessel, RMLV, sent a weather report on 4619.5 kHz CW 28SEP2026 at 1808 UTC to Russian Navy Northern Fleet Naval Base in Severodvinsk, RJD99 RMLV at position 64.9N 38.5E heading North West at 6-10 knots RJD99 answered on 6259.5 kHz

RCQE 132 17 16 0905 132 = FOR RJH82 RJZ4 = 16061 99660 10394 41498 92306 10080 40130 51010 70102 8741/ 22252 20101 88000 80000 16014 AR RCQE K

Unknown Russian Navy Vessel, RCQE, sent a weather report on 4537.5 kHz CW 16SEP2026 at 0615 UTC to Russian Navy Northern Fleet Naval Base in Severodvinsk, RJD99 RCQE at position 66.0N 39.4E heading South West at 6-10 knots RJD99 answered on 6007.5 kHz

RMHW 130 15 13 1805 130 = FOR RIF4 RJH82 = 13151 99693 10349 42698 41608 10138 40048 57008 82401 22200 00112 20201 13012 = AR RMHW K

Russian Navy Hydrographic Ship Romuald Muklevich, RMHW, sent a weather and report on 6290 kHz CW 13SEP2026 at 1509 UTC to Russian Navy Northern Fleet HQ in Severomorsk, RIT RMHW hove to at position 69.3N 34.9E RIT answered on 5343 // 7467 // 11155 kHz

At 0643 RIT sent message to RMHW: RIT 773 35 12 2042 773 = SML = 22222 (5LG ... ) = AR RIT K

At 0640 UTC: RMHW 803 16 13 0905 803 = FOR RIF4 RJH82 = 13061 99692 10361 42798 21608 10105 4007_ 57022 70100 82040 22252 00104 20201 _____ = AR RMHW K

At 0638 UTC: RMHW 531 14 13 0605 531 = FOR RIF4 RJH82 = 13031 99691 10366 42998 01506 10104 40098 57015 22272 00104 20201 13011 = AR RMHW K