Meaning of numbers on Hiatt handcuffs UK

Hello all,
I'm currently researching some handcuffs that were handed in to our local museum. 
They are both Hiatt, one figure of eight style numbered 13 and one pair of chain handcuffs numbered 394 with an 'A' stamped on the end of the lock barrel.
They came to us from an ex-policeman's relatives.
Can anyone provide approximate manufacturing dates?
Does anyone know if the numbers are model numbers or perhaps local serial numbers?
Thanks
Kevin

Hi Kevin, if you let me know what museum you are I will send you a complimentary copy of Alex Nichols book on Handcuffs which has lots of info on Hiatt and dates. The serial numbers on your cuffs do not refer to model number or dates.

It is said that the 'A' or other letters were used to record which worker made the cuff.
It looks as though the numbers were stamped prior to plating in the manufacturing process. One reason is to match the cuff to the key, because all keys are not the same. 
The design and manufacture of these cuffs remained much the same over 200 years but these look to be made mid 1900s. Later ones often had cast bows, not hand wrought.

CHRISCUFFS wrote: ↑

Dec 17, 2023

Hi Kevin, if you let me know what museum you are I will send you a complimentary copy of Alex Nichols book on Handcuffs which has lots of info on Hiatt and dates. The serial numbers on your cuffs do not refer to model number or dates.

Thanks, I'm doing some research for an upcoming exhibition at Thame museum, 79 High St, Thame OX9 3AE
https://www.thamemuseum.org/