RE: OS10 FSR
The OS PET was loop scavanged, while the later FSR is schneurle (iron/steel) and after that came the FP (early ones can be iron/steel but later ones are ABN) and the latest is the LA (also ABN). The FSR has a failry large boost port, it is then smaller going to the FP and then none on the LA (don't have one myself though).
The "fake" port/bulge on the case just gives them something to put the logo on, that's all. The real ports are rotated compared to the outside of the case, this also shows from the position of the exhaust port.
Here are some pictures with the FSR to the left (in both pictures) and the FP to the right. The FSR lacks an adjustable airbleed, but has the bulge for it...