I like to use the clip-on meters with the early non-metered SV, H1a, etc. even though they add bulk to the camera. They couple to the shutter speed dials, and let you simply read the nominal f-stop from the top, where it is easy to set the lens appropriately before raising the camera. I find I don't "over-tweek" the exposure with an external meter like I tend to with display in the finder, so I get better timing on my shots.
The original "Round Top" meter is very nicely made, and I like it better than the subsequent "square top" meters, but it's hard to find this early model that still works.
I had found a couple that were pristine, where the meter circuits worked fine (per the battery-check response) once the switch contacts were cleaned, but they barely reacted to light, and then only on the "Low" setting. I finally found one that works very well, and then noticed the difference while looking at the CDS cells. The one that works well has a clear coating over the cell so you can still see the circuit grid as you normally can on meter cells.
On the ones that don't work it looks like the cell coating has darkened and turned opaque.
I'm going to experiment to see if this is a surface coating issue that can be cleaned, or if I can find a suitable replacement cell.
In any case, if you find one of these meters, unscrew the front lens and switch the meter to "Low" so you can see the cell. If it has turned opaque, it won't work properly.
The later Square Top meters don't seem to have this problem, and usually can be made to work well by cleaning the switch contacts inside.