Smith Wesson M-100P

I came across this pair of handcuffs at a local pawnshop for 20 bucks and as a new collector I haven’t seen any S&W with a extended chain like these. I have a few questions.
Where these made at the factory like this or somebody did it after they bought it ?
It has a serial number of 451605.
Is there anyway to find the date of manufacture by the serial number ?



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sigman,
Smith & Wesson offered special order restraints to anyone who wanted to pay the price.
In a S&W product guide dated June 2008, they offered their Model 100L that had a 4-link chain.
I don't have a product brochure that advertised a longer chain Model 100, but in 2010 I purchased from a S&W distributor a long chain Model 100P (push-pin double lock) that had  a 10-link chain. It came in a slightly larger box.
Dave