The Marlin model 30 was often marketed as the Glenfield Model 30. Basically, it's a 336 with a hardwood (non-walnut) stock and simpler sights.
They were sold primarily through discount chains. (For example, in Oklahoma's OTASCO stores, there was a series of Model 30's sold with custom model numbers--3080, 3081, etc., where the last two digits were the year of sale.)
There were several evolutions; the 30, 30A, 30AW, 30TK, and 30AS come to mind, though I'm sure some true expert will be able to name some others.
Great little rifles!
