Data plate mounting.

[user 30038]

My A&P says I need to mount my data plate outside the aircraft. Both planes have gone their whole life (20+ and 35+ Years) with the plates inside the cockpit viewable from outside. I know what the Regs say and have seen other planes with same mounting.
How can this be? How did they get Special Airworthiness Certificate if this isn’t legal? How have they gone the whole time without being cited?
Should I mount outside?

 

[TFF]

 

[Dan Thomas]

 

[user 4289]

 

[Pops]

 

[mcrae0104]

 

[user 30038]

 

[X3 skier]

 

[pfarber]

 

[Dan Thomas]

 

[Pops]

 

[Dan Thomas]

 

[user 30038]

 

[cluttonfred]

 

[Pops]

 

[TFF]