Rick,
I went and looked at my sparse catalogue accumulation and it looks like the early Model 4 used a bolt safety as well. The '36 catalogue shows a slide safety for the Model 5, but doesn't hype the rifle as a new model. Curious.
When did Savage and Stevens combine their catalogues? Not prewar as near as I can tell. My 1948 catalogue is the first I have where it showcases both lines.