The green is really a laminated board painted grey. The noses of the bullets are resting on the kind of velvet-like covers sold at shows for display cases. Since posting this I have found a few more base marked bullets I had. Not quite filled yet, but closing in on that...
Before this, most of the bullets had been displayed butts up in that floral foam flower arrangers use at the bottom of vases. No ill effects were observed from several years in that substance.