Newbie needs help

[D. Ricks]

Here are pictures of the mags and front serial # dju. Took these in the bright sunlight. There are a couple small scratches by serial #.They are nickle and look like originals I found on line searching this gun. The # 2 mag's base is darker but the numbers stamp look the same. Does anyone know what the K&B stamp in the frame means? Thanks for all the info. and compliments. Like I said I mainly collect Third Reich guns etc. but could not pass on this one. Thanks to dju,Andy,Don and Ed. Regards Dail