Glass Implant Fixture: Any Thoughts?

Dr. R. asks:
Please see the photo below. I removed, after 20+ years of successful service, what appears to be a glass implant. It has approximately the weight and density of glass, as opposed to resin, and clarity to match. The patient is a woman who just turned 90 and does not have much recall of the procedure, the product, or the dentist who placed it. Having never seen nor heard of anything like it, I thought I’d put the question to the forum: What is this? Who made it? In what time span was it likely placed? Assuming the main reason for its failure as a product was lack of bio-compatibility, are there any other reasons for its demise?

Implant perched on pre-removal x-ray