After searching many information of vintage step attenuator 
for use in my tube preamplifier.
I’ve found attenuator in the box that use Tech Lab 600 Ohm attenuators.
Tech Lab Inc. was made high quality attenuator like Daven did,
that use in audio and measurement products like Western Electric, Tektronix, etc.
Stereo Sound Japan was provide information of 
Tech Lab PK-322 that has 2 types of resistor inside.
Type I : Mold Resistor & Winding Resistance Type

Type II : All Winding Resistance Type

Attenuator in the box from Stereo Sound Japan 
was use in many test system of Tube Kingdom magazine.
Like Stereo Sound Japan Website recommended.
Type I attenuator matched with all popular and modern music and 
Type II attenuator matched with old school music like Blues, Jazz and Classical. 
Both types improve dynamic and detail of sound system a lot. 
Let’s try !!!