Jacksprat re the Costa Mesa/Howa AR-18/180 bipods I doubt that ArmaLite would of used a Colt marked bipod. I havn't discovered any bipods with just ArmaLite markings. Two bipods would possibly be good candidates for the AR-180, one is the first shorter AR-15 bipod and the second is the same length as the standard Colt bipod both minus any markings. The later Sterling bipod was plastic, Rick has a photo of it on his blog. Same thing applies to a bayonet and sheath, the most appropriate would be contract examples. Again with the addition of the rare ArmaLite 4x20 scope Rick has assembled an outstanding source of info that he has so generously shared with us both here at AR-15 and his blog.