z61t base frame numbers

[Paul_L]

I need a bottom frame for a Z61t. The frame in the computer is labelled 42W3544 but looks identical to a 42W3125 which is available on eBay. The manual I downloaded from the Lenovo site has three possible frames, the 41W4844, 42W3123 and 42R9957. As you can see neither the frame in the computer nor the one for sale is mentioned in the manual.

Anyone know if the 42W3125 is a universal replacement? I have come across this sort of thing in parts for other equipment.