A lithium ion-conductive solid electrolyte including a freestanding inorganic vitreous sheet of sulfide-based lithium ion conducting glass is capable of high performance in a lithium metal battery. Such an electrolyte is also manufacturable, and readily adaptable for battery cell and cell component manufacture, in a cost-effective, scalable manner using an automated machine based system, apparatus and methods based on inline spectrophotometry to assess and inspect the quality of such vitreous solid electrolyte sheets and associated components. Suitable manufacturing methods can involve multi-stage thinning of a sulfide glass preform that includes a first thinning operation that involves applying a compressive force onto the preform to form a glass sheet and a second thinning operation that involves applying a tensile force on the as-formed glass sheet (e.g., drawing the sheet by pulling).