Not to further nitpick but the Randall was mfg. between June 1983 and May 1985; according to the Blue Book Of Gun Values.
They did not list the production dates for the Hardballer in the Blue Book I have but the one line Probert Encyclopedia lists the production start date as 1977. Also every AMT 1911 type pistol I've ever seen has had stainless used in all the parts I could see not counting the rear sight.
Speaking of stainless parts and sights I have a further comment on the AMT and Randall slides looking alike. The front sight's are 100% identical and the slide serrations match as they are vertical.
They seem to be more copies of each other, minus the rear sight and milling for it, than copies of a Series '70 Gold Cup slide. I'm not implying any dirct connection between the two companies but rather that they both might have contracted another company to produce the slides. Out sourcing parts is not unheard of in the firearms industry.
On a different note, I noticed that back when they were both being made the Randall had a higher suggested retail price than the AMT. Which most likely reflected a much higher QC in production.