Pictures would help. Are you saying that the arm is removable? Because, before '60 the arm could be removed or folded down by losening the thumbscrew that held it on. In '60 and '61 the arm was riveted on, so unless you drilled out the rivet, it's not removable. Starting in '62 the arm was not removable. It was all once piece.

This guide shows the differences.

https://www.vintagedrumguide.com/drcjw/article_5_strainers_3point-10.html

Thanks for this info. 

This is the strainer below

Why did the Leedy version have a ring of leather? Was that to keep some vibration sound down?

Another question, does your drum have the extension gates on each side? Or is it just the strainer on one side, and a regular butt on the other?

Radio Kings or Artist snares as they were later named, had the extension gates, and were usually, but not always, single ply shells. 

Student Radio Kings had just the straner and standard butt and was a three ply shell, except for an occasional odd ball with a single ply.

Also, if it has the extension gates, then the slider will be bent outward and have either  a single screw hole in the center, or the screw hole and two small holes towards the end.

If it didn't have the extensions, then it will be bent inwards with 11 or 12 holes as your straner has. 

Your strainer is correct for a Student Radio king, but the arm shouldn't be removable.

If your drum is truly a 60s drum, then that is the incorrect strainer other than the slider. It is for a mid to later 50s drum.

This strainer is correct, although it has the slider for a Radio King or Artist drum with the extension gates. The arm, however is correct. The sliders are interchangable however althogh yours looks to the nickle and the one on Reverb is chrome. Will certainly work, and Slingerland did sometimes mix and match.

https://reverb.com/item/80943061-slingerland-3-point-strainer-1960-s-worldwide-shipping-chrome

rimshot99's strainer is later 50's/very early 60's as thin shell stated above.  It is for a drum without snare extensions.  There have been reproduction lever/arms available or you will need a used original.  Check Reverb/eBay etc.  The correct lever/arm for yours would be without the "Slingerland" stamp.

Rik_E, I believe what you are referring to is the gum rubber washer that was added in ~'62 to the 3-point strainer.  This kept the fine tension knob from unscrewing and provided a friction lock to help hold the strainer engaged.  Used on other Slingerland strainers also.

I should have mentioned that those strainers were also used on Leedy snare drums once Slingerland bought them out. They were used on the 50s and early 60s Reliance and Utilty models which also didn't have snare extensions.

There is a small groove in the tension shaft which should have an aluminum ring, which is missing, but an E clip was used later so any well stocked hardware store should have one that fits.