I just handled a 577 Gibbs 3" double made by Gibbs turn of the century. Is this the same round as the 577 NE? The brass was old Kynoch. Thanks.

Maybe. What did the proof marks say? The .577 3" was also loaded as a BPE. The ammo could have been loaded for Gibbs by Kynoch or Eley and so was headstamped Gibbs, a common practice. Little doubt that it is the same case, but only the proof marks on the gun will tell whether it is Nitro or BPE. Gibbs didn't have a proprietary .577 3" that differed from the standard trade round.
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"Serious rifles have two barrels, everything else just burns gunpowder."

Thanks for the information. I suspect it is the Nitro round though the caliber engraving clearly read 577 Gibbs 3". Apparently one of only a few made.