Hi Roy,
I suspect that the variation, particularly with the shortened 5 shot mags is due to each maker cutting down a standard 10 shot magazine and then putting their own finishing touches on them. As far as the 10 round mags are concerned, over the time frame that Commercial Lee Speeds were available, there were quite a few modifications to the standard 10 round mag.
Just my thoughts. I have cut a military mag and turned it into a 5 shot myself to use in my BSA Sporter that came with a 10 shot one.
LesLeeSpeed.