Seeburg L models, also known as the Seeburg Junior, used three
different types of pneumatic stacks.  The most common stack is the
two-tier stack of the 1920's.  The valve travel is .035 with leather
facings.

The valve covers sold today are not correct.  They may look good but
you need to measure them.  The new ones were made deeper than the old
ones so that the current maker could sand them to fit depending on the
thickness of the leather facings.  The original valve cover was 0.242
inches thick, top to bottom, plus or minus a couple of thousandths.

Don Teach
Shreveport, Louisiana