There were twelve bells in the box in all in about 1969 (the other two were the interlocking bells to Ferme Park South Down and Harringay Up Goods for the jointly bolted/worked crossovers, Down Slow 2 - Down Goods, and Up Goods 1 - Up Slow. I can't recall whether they were also up above the windows on the back wall.FINSBURY PARK 5 wrote: " .... i particularly remember from my visit to the box in early 1973 was ..... the S&T department had mounted about 10(?) wooden cased block bells high up along the back wall of the box with long chains attached to each individual bell so that when the block bell was rung by another box the signalman could see which one it was with the chain 'dancing around' for several seconds all the 'pegging' block instruments & tappers were mounted on a normal block shelf above the lever frame. .... "
Yes there was certainly an array of various chains and strings (about 1 foot? long) hanging from the bell hammer stems for the reason you mention [and IIRC, an unrivalled (in this area), astonishing variety of (exposed) bell/dome types] ; [ These bells were all mounted so that their bell hammers moved in a horizontal plane, apparently to impart maximum possible movement to the hanging strings, chains etc.].
The block instruments were all of the Tyers 'black box' type, with in-built bell key/'tapper' (used here for the bell circuits of the block sections in rear), and there would certainly have been scope for confusion if the usual 'on back of the casing' bell on each had here been used for the section in rear, as (IMHO) the variety of tones found amongst them was more limited compared with those of normal GN types of bell.
The bell keys for the advance section bell circuits were of the small wooden plinth-mounted, fully-exposed type, resembling a simple Morse sending key, as used in several boxes on the route where shelf space was at a premium; (e.g. Hornsey No.1) : Here at Harringay West ('Passenger') box the shortage of block shelf space over the 40-lever frame was partly owing to the space taken by the seemingly numerous lamp repeating indicator/bell/switch units.
Do you also remember Mickey, because the signals fitted with lamp repeating had it done by means of the combined arm & lamp repeating circuit method, that while the arm repeater of any of them was showing "WRONG" (i.e., neither "ON" or "OFF"), the 'lamp out' trembler bell would ring continuously?
This meant that the box was slightly less noisy if the levers of those signals so-equipped were not thrown/released back in the frame more quickly than necessary behind passing trains, because, as may be expected, the more rapidly that each of these signal arms dropped back to horizontal, the more times it bounced until settling in the ON position, and so then its bell would ring during every bounce of the arm.
I was shown something similar at New Southgate.FINSBURY PARK 5 wrote: " .... The other thing i noticed was 'alittle trick' Norman showed me with regards to the levers on the Up slow line?. If Norman closed the catch handles on the Up slow line Inner distant signal lever and the Up slow line home signal lever [etc.] .... when Norman put the Up slow line outter distant signal lever fully back in the frame suddenly the Up slow line inner distant signal lever would first fly fully back in the frame followed by the Up slow line home signal lever as well as the Up slow line starting signal lever it basically saved the signalman putting each individual signal lever back in the frame one by one, a neat little trick i remember thinking. "
There, there was a shunt move possible from the 'station yard' (just south of the box), straight onto, and back along, the Up Goods in the Down direction, then crossing to the Up Reception at the north end of the station via No.56 points, and continuing north towards the 'Top Yard' (between Cemetery box and N.Southgate). This involved four disc shunting signals (27, 35, 46 and 55, IIRC), with each being released to be pulled by the one next ahead being cleared first.
Like you say, in this case, once 27 was fully Reverse, if the catch handles of the other three were then closed, leaving their levers held Reverse only by the lever (inter)locking, then putting 27 back to Normal allowed the weight/tensions of the other three to pull their levers quickly back to Normal in sequence, untouched by human hand.
In my opinion, more a novelty than being of much practical use, and creating risk of premature or accidental initiation if done while there was a real movement in progress. (But still impressive to visitors)