With the CHR 27-70 Q, there are three series of movement designs. Other sources differ on the date ranges, but this is what my research found. From 1994 to 1996/1997, there was a large, unsigned, oversized “block” bridge over the rattrapante wheel. That block, which was vertically grained, resulted in functional issues with the reset mechanism and the isolator failing to engage properly. Patek offered to replace that bridge, so these are rare, and even seasoned collectors and dealers might never have seen one or might think that this was some aftermarket job.
The second system, used from 1997/1998 to 2001, is a more delicate, shaved-down bridge attached with only one screw, still meeting at the center post. The bridge has a bit of a dogleg shape, with the end seemingly attached to a pin that goes into the rattrapante plate. After 2002 (though some say 2004), the third series was developed into a more secure final form, held down by a screw passing through the isolator, thereby preventing flexing. Any era of watch could have been updated during Patek servicing to the final design, so date ranges don’t reflect what you should see, but what you could see. One other thing to note is that later era movements seemed to oxidize for some reason, and often need a clean-up during service.