I had a conversation yesterday with the person from whom I got my original Obi lightsaber blank back in 1997. If his memory serves him correct, there were about 8 mechanized sabers build in total for ANH plus some "static" ones without the spinnung function. He had built not all of them himself.
Here's a still of that lightsaber blade darting out of the hilt from ROTJ:
View attachment 966195
Could this be a blade similar to this one?:
View attachment 966196
That would mean the "tang" of the blade would go right through the balance pipe, vent and grenade section into the clamp/booster section of the saber.