Background: I sent to Veral an order for three molds including my 1895 .50-110 Square Bolt. Ordering a 300 grain mold, he sent me a 335 grain mold since it fit the rifling better. Calling and taking to him, he knows the varying forms of Marlin rifling and built molds to the rifle. This rifle was Ballard style with deep grooves and he built the mold accordingly. The mold shot well.
Strictly speculation: These molds may be made for the shallow-groove Modified Micro-groove rifling which Marlin offered. Marlin made a first run with conventional rifling barrels to test the market, then a short-run of 16-groove barrels since the market was there, then the Modified Micro-groove 12-groove barrels for cast bullets. The Modified Micro-groove barrels are slightly deeper rifling with square corners on the lands.
I've shot a friend's 16-groove 1895 with cast. We were shooting 405 grain bullets cast at .460 to fit the leade, wheel-weight alloy, at 1500 feet-per-second getting 2 minute-of-angle five-shot groups. Marlin eventually went to the Ballard-style rifling to appease the gun magazine writers who know nothing about fitting the chamber leade and not the barrel.
This reinforces my thought most gun magazine writers know nothing about cast bullet shooting. (They produce Masculine Bovine Defecatory Material)