It is hard to get info on the Irwins.
I just bought a 1973 32' and researing that I could only find the sails brochure.
There is an old employee of Irwin that has some info on the web, the link http://www.irwinyachts.com/aft-cockpit_files/AFT1.htm
show both the 25' and the 10/4 (also 25') brochures.
I was suprised to find out that the Endeavor 32 was the same as my Irwin 32.
I believe when Irwin stopped producung the smaller boats in the 70's some other companies picked up the design like the Endevour 32 and Lancer 25.