The records are sketchy at best for most modern BP guns as far as manufacture dates. Many of the CVA guns made in Spain have a serial number that looks like this; 492.1234567 this would be a tell tail for being made in April of 92. as for general dates they were made from the late 70s to 1995
MMO Grinder - 2011 Hawken 3-6 was released on: USA: 16 April 2013
Georgia Outdoors - 1992 Black Powder Deer Hunt 4-8 was released on: USA: 1994
Independence U-S-A- - 2012 Black Powder Rifle 1-8 was released on: USA: 7 March 2012
Chicly Geek - 2012 Anime Expo Interview with Hawken the Video Game 1-5 was released on: USA: 4 July 2012
Powder TV - 1991 was released on: USA: 1991
Powder - 1916 was released on: USA: 10 February 1916
The blue book of modern black powder values has information on dates, manufacturers, and a wealth of other info on Daly and others. It may help. The book is available on line free to NRA members at www.nragive.org or from sporting retailers like midway USA and Dixie gun works.
To find the age of Pietta guns you would need to know the model and serial number, The blue book of modern black powder values has a section in the back listing manufacture dates based on this. Or let me know the info and I can give you the year made.
Heating Powder - 1908 was released on: USA: September 1908
The Marvelous Powder - 1908 was released on: USA: January 1908
Paint and Powder - 1921 was released on: USA: 6 March 1921
He Took a Powder - 1955 was released on: USA: 27 October 1955