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Here's a start.

FAQ section. (Frequently Asked Questions)
http://www.whalercentral.com/faq.php?...p?cat_id=5
http://www.whalercentral.com/faq.php?...?cat_id=10

The links above also have links to the Whaler Model Specifications section which is also on the left sidebar.
http://www.whalercentral.com/userphot...allery.php

From your Stencil number, It is not a Montauk as the first Montauk was not made until 1973.

That should get you going in the right direction.
Let us know what you find out.