Several model manufacturers produce plastic display cases. I haven't seen one yet without that annoying moulding nipple, or dimple, right on the top of the clear cover . Are there any without? Can't any of these clever companies, who make good model kits, make a decent display case?

Sadly, it's the easiest way, to gate (injection nipple) at the top center of the cover. Back in the 80's a vendor suggested we could simplify one of our housings by gating at the center of the cover, then milling off the gate and covering it up with a small round sticker.

It might be possible to gate the part along one of the edges. But it may result in a long distance to "push" clear plastic all around a case large enough for a 1/48 fighter. Resulting in longer cycles and more rejects -- thus higher costs. If they gate on two opposite edges, they could get a 'weld' line where the two flows come together, which would be more obnoxious than the nipple.

Not necessarily ... with a properly optimised cycles this should be all but invisible. Ive seen many largish transparent items where the weld line is only visible when holding the item at an angle. Extra gates will more than likely push up the price too much.

I went to the dollar store and picked up a clear plastic butter dish for a couple of bucks. It's the size of a brick of butter - too small for most models, but the point is if this butter dish can be moulded cheaply with no nipples or dimples, why can't model display covers be moulded similarly?