You posted on "General Parker Discussions". There is a "Parker Hammer Gun" section next down which is full of hammer guns with hooked or fishtail top action levers. You'll see many guns there like yours.

Your gun appears to be in original finish and quite well cared for.

Just for clarification...

Annual PGCA Membership is $40

PGCA Research Letter for a PGCA Member is $40

PGCA Research Letter for a non-member is $60 (currently)

Suggest you order your letter soon.