[WVsig]

I am not sure how I missed this thread but the 511 prefix was used by FN for both Browning and FN rolled marked guns between 1998-2017. It was a change to be compatible with their new inventory software from Oracle. IIRC ones with odd rollmarks first showed up when FN did a run of FN rollmarked guns for the US market. They did not sell well and were liquidated by CDNN. FN choose to leave the BHP under the Browning name only in the US. The 511. prefix was for 9mm the 513 was for 40 S&W.

Later odd ball roll marks occasionally showed up on 511 or 513 prefix guns. If I had to guess they were left overs from the FN runs and they were using up parts. This accounts for the non typical rollmarks on the right side of the slide.

This particular one is odd because it is parkerized not blued or polycoated. To the OP take a pic of the box label. It might tell us if it left the factory parkerized vs one of the other finishes. FN always broke their own rules when it comes to standardization and they never threw away parts. It could have been part of a small contract run which called for a park finish or it could have been leftovers from an older contract which was never shipped. Interesting example thanks for sharing.

My BHP knowledge has been kindly overstated by other members. These are just my WAGs based on some research and buying, selling , trading and customizing a lot of BHPs.