OTK marked bulgy orange bayonet

Just noticed that my Bulgy orange bayo has an "OTK" mark on the scabbard. Also, it appears the bayo handle and scabbard was ground down in two places. Was this a Russian bayo scrubbed by the Bulgarians?

Just noticed that my Bulgy orange bayo has an "OTK" mark on the scabbard. Also, it appears the bayo handle and scabbard was ground down in two places. Was this a Russian bayo scrubbed by the Bulgarians?
The OTK marking is a Russian quality control marking. So it appears it is of Russian origin.

Here's a circle 10 Bulgarian-made bayonet marked "OTK".

http://tantal.kalashnikov.guns.ru/bayo3.html

Here's the Soviet OTK marked bayonet.

http://tantal.kalashnikov.guns.ru/bayo2.html