I Need a little help as I don’t want to ruin something . I need some input on disassembling the sight-glass from the cast iron top and bottom. Got the bolts loose but the top lid of the sight-glass won’t pop loose from the glass . I didn’t want to force it so I stopped . Are the glasses cemented into the top and base cast pieces looks a visible glass cylinder or ? Don’t want to break the glass as it is all original . So any help from someone who has disassembled one with success that would chime in and help quite do this successfully would be greatly appreciated . Googled site search but found nothing on this . Thank you . Picture for reference of the sight-glass .