I think this is a Penn reel that I bought 60 plus years ago. The only identification I could find was inside the side plate with numbers 12-570656 and 656075-21. The side plate diameter is 4 1/4 inches.
(http://i34.photobucket.com/albums/d126/walkernut/DSC_0604.jpg)
Looks like a Diawa. Made in Japan. Sea line ? If you can work on a pen you can work on one of these ........ very similar inside.
Todd
Yeppers you got it.!!
Daiwa Sealine 600H.
Its an excellent reel.
The 600H is a great reel.
We have upgrades available. Stainless Sleeve and Carbon Fiber Drag Kits take care of the weak links.
http://alantani.com/index.php?topic=14486.0