Voltmeter & One way key

        VOLTMETER :                                                               

 Voltmeter

Black plastic material values are given below: 

In above image, Diffuse BSDF is used & the scale is applied as image texture. In this red terminal, add Diffuse  BSDF & give R=0.168, G=0.01014 & B=0.000 
                         

                          

One way key:

The one way key's material is same as tap key. I have put mix shaders to get the result of Black plastic material of key. One is Glossy BSDF & other is Diffuse BSDF with roughness as 2.000 & 0.000 respectively.