Lol!!! XD
Out of interest, what happened at that time to make it so special?
each digit changed individually, so on the 10 seconds you got 2 clacks, on the minute 3 clacks, 10 minutes 4 and so on. At 09:59:59, 19:59:59 and at 23:59:59 you got 7 clacks as each digit changed but it took almost a second for all 6 digits to change the next second then kicked in!
so the time board would have shown this:-
09:59:57
09:59:58
09:59:59
09:59:50
09:59:00
09:50:00
09:00:00
00:00:00
10:00:00
10:00:01
10:00:02
and so on.....
using the standard 7 segment digital number display the loudness of the clack depended on how many segments moved. 9-0 and 2-3 moved 2 segments and was relatively quiet, 0-1 and 3-4 moved 4, 5-5 and 8-9 just one being almost silent but 1-2 and 6-7 moved 5 segments and was the loudest!
made the NSE clock very distinctive sounding! Almost mesmerising...