casement window crank

A home owner from Upstate New York says:
Opens left. Arm seems to measure 8" from the bend to the opposite end. Screw holes seem to measure 4-3/4" for the outer holes and 4" for the inner holes. (I'm not great at measuring.) This is to replace a crank on a steel-frame "architectural" (?) window, it has multiple small panes, it's probably from the 1940's. I do not see any markings, names or numbers.
Thank you.
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Bob from SWISCO responded:

This appears to possibly be our 39-353 & 39-354 Hope Operators. Please compare the dimensions and see if you concur. 

A home owner from Upstate New York says:
The 4-1/8 on center looks correct; however, from gear center to arm button is only 8" or possibly 8-1/4".
I'm confused about this because we've previously purchased replacements for these casement cranks from you and I see in my archive they were 9" arms. But this one definitely measures 8-8-1/4" not 9".
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Dave Sr. from SWISCO responded:

At one time operators were made with a 8-1/2" long arm. However it seems that now the norm is 9". Check your casement window. See if it is wide enough to accept the 9" long arm. Take the measurement from the center of the operator like they show on our website. Also, looking at your photos it appears that you have 4 mounting holes. Check the difference in the mounting holes between the 39-002 and the 39-353 to see which one matches up to the mounting holes in your operator.

39-001 : Window Crank Operator, 9
Window Crank Operator, 9"
39-001
$16.38
VIEW >
39-002 : Window Crank Operator, 9
Window Crank Operator, 9"
39-002
$16.38
VIEW >
39-353 : Hope Operator, 4-1/8
Hope Operator, 4-1/8" HCs
39-353
$23.25
VIEW >
39-354 : Hope Operator, 4-1/8
Hope Operator, 4-1/8" HCs
39-354
$23.25
VIEW >
Anatomy of a casement window
Anatomy of a casement window
VIDEO
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