Thank you for your reply. I'm sure it's not wood but metal and there are no other hallmarks. In the third and fourth image, in the lower left corner of the center crossbar and at the bottom of the longitudinal axis there are two exposed faces, without metal, that have the texture of the stone.
if you can not then it is not necessary to clean. I don't think that Athos cross at the base. thread in the original simplified. Maybe Kiev-Pechersk Lavra. On the front side in the middle of the Crucifixion of Christ with the upcoming, in the upper beam under the crucifixion and selected saints. At the ends of the rays of the Evangelists. Turnover in the crypt of the Epiphany, in the upper beam of the Lord of hosts, the ends of the left and right beam Peter and Paul, under the scene of the baptism of someone of the elect saints in the lower beam of the Evangelist.
Write through the online translator, so do not judge strictly.