Also, the Milt Sparks Summer Special is an AIWB-intended holster.
"The ubiquitous Milt Sparks Summer Special, first developed by Bruce Nelson while he was working undercover, was originally an appendix holster
(for a Colt Commander). That's right, the granddaddy of IWB was an appendix rig. AIWB was used extensively -- with and without a holster -- by many plainclothes and UC law enforcement officers for a very long time."