welcome to the board
it's a Grade 0 12 ga - from what I can see the bores look good
a careful cleaning - no abrasives would not hurt it - Frontier
https://www.big45metalcleaner.com/ work good on metal
as for shooting it - no one can tell you that from pictures (which BTW you did a better than the average new poster job with ) it would need to be inspected by someone who knows old doubles - maybe one of the members can recommend a smith in your area
the L in not part of the weight
repro butplates are available
restoration would, not be worth it IMHO
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