I will take a shot at this one, pardon the pun
Lew Horton is a big firearms distributor in Massachusetts. They are pretty smart folks and found that there is a market for non catalog guns. So they contract with Smith & Wesson and other mfgs. They make runs of guns with different features, calibers, barrel lengths, porting, grip frames and combinations their of. Most of the runs are limited some around 5000 pcs. So they are desirable if a combination of parts strikes a cord with buyers. Like 3" N frames with .4X calibers.

I was told by a S&W salesman that LH got the idea to have S&W build these because people were modifying them or gun smiths building customs, he made mention of the John Jovino mods, like the Effector I suppose.
I was also told the S&W was very hesitant to make the first batch. So they wanted the order to be for One Million dollars worth of guns hoping to dissuade LH. They did it anyhow and the rest is history.

I think the first was the 24-3 3" 44spl

Thats how I know the story to be not sure if its 100% true or folk lore mixed in...