Okay, 'been searching up and down and it's pretty hard to come by a 452 Ultra Lux or the 452 Training rifle in .22LR -- both appear to be the only 452s that have the tangent sights it seems (pls correct me if I'm mistaken). The very few I came across are priced higher, a couple are even above suggested retail price.
A post from June 2010 discussed differences between the 452 and 455 American, so that gave me information on the differences between the 2 in terms of their construction (bolt, receiver, sear, trigger guard, etc.). However, feedback on accuracy, performance, and reliability on the interwebs is rather mixed, so... I'm taking those with a grain of salt.
Now, with the 455 UL and 455 Training rifles, both with the excellent tangent sights, is there any reason why I shouldn't go for one of these instead? Is there a significant difference between the 452 and 455 in terms of accuracy or reliability?