Used lightly K101. Rare bird. G spot stamp. These are unique as far as these are the first Bulgarian 556 import AK pattern receiver. The receiver is a 100% finished Bulgarian SLR 100 receiver marked K101 instead and imported from Bulgaria. AUSA then contracted Gordon to build it out with NOS Arsenal parts. A very small run of SSR 99s and K101s exist. Less than 300 and half of that are Gordys. Interestingly the receiver is finished in Bulgaria which is the only 556 milled Arsenal receiver that is. SA-M5 is an %80 finished in Vegas and the SAM5 along with all current SAM is machined slightly differently in the rear which has caused bolt deformations. It cant be 100% Bulgarian but im not sure how they get around it. I think like saiga by not installing a bullet guide. Anyways, ask questions