What does Ref-A-M in Sgl Ref-A-M Clr 6mm on BCL stand for?

Same for Ref-B in Sgl Ref-B-H Clr 6mm.

What does Ref-A-M in Sgl "Sgl Ref-A-M Clr 6mm 6mm window" on BCL stand for?

Same for Ref-B in "Sgl Ref-B-H Clr 6mm" ?Sgl Ref-A-M Clr 6mm Sgl Ref-B-H Clr 6mm.

What does Ref-A-M in "Sgl Ref-A-M Clr 6mm window" on BCL stand for?

Same for Ref-B "Sgl Ref-B-H Clr 6mm" ?Sgl Ref-A-M Clr 6mm Sgl Ref-B-H Clr 6mm

What does Ref-A-M in "Sgl Ref-A-M Clr 6mm window" on BCL stand for?

Same for Ref-B "Sgl Ref-B-H Clr 6mm" ?Sgl Ref-A-M Clr 6mm

What does Ref-A-M in "Sgl Ref-A-M Clr 6mm window" on BCL stand for?