On checking some of my Fed 1b, I came across this one, with plenty of engravings inside... It's the # 25617, with the so called "lizard" vulcanite.
http://www.ussrphoto.com/UserContent2/542024_IMG_1510.JPG
Inside, at the back of the speedbox:
http://www.ussrphoto.com/UserContent2/542024_IMG_1491.JPG