The 3 point strainer has different adjustment knobs, After seeing this pic yours is a late 30's to early 40's model

Here this will help you a lot great info here. http://www.vintagedrumguide.com/drcjw/article_5_strainers_3point-1.html

Thanks - that's really helpful. Going by that guide, my throw seems to be mix of the '28-'34 and '36-'38 pictures; The multi-hole slider flange faces inwards but the adjuster knob has vertical knurling lines. I see that the inward flange continued until 1958 but only on snares without an extension arm. Very interesting.