It's certainly not common, though I've seen two used EL SV’s for sale with the focuser cover missing
(one had a white plastic screw cap as a replacement!).
As can be seen the focuser cover (along with the marked end cap) slides on over the complex underlying mechanism,
though it's not clear how it is retained:
The complexity is necessary to translate the rotation of the focuser knob, to a front and rear motion to move the focusing lenses,
taking into account the very small space in the bridge arms.
(Contrast that to the relative simplicity possible where there is a full length bridge such as with the Leica Ultarvid HD,
as shown in posts #8 and 15 at:
Sticky Focus Wheels )
The original EL has 270 components, and while the EL SV's focuser was much simplified, it still has around 170 components.
For more, see posts #49, 52 and 60 at:
Binocular Weight, a Triviality?
I’ve also attached a full copy of the EL SV image below.
John