Anyone know about these....

I was actually looking for pictures of original Dynaco's to see if the one I have is actually a real one and I ran across this. It seems to be a easy way to add a headphone jack to a amp. It's made by Lafayette but they seem to be out of business now. Looks like the headphone jack was made to be there. Maybe it was, was that a option when ordering a kit?

Does anyone know if someone else is making these anymore? I wouldn't mind having a headphone jack at times and this seems easy to install one, and I need easy. I'll try to post a pic. 

I would advise NOT to connect headphone to a power amp. Reasons are two :
1 / it could permanently destroy your hearing as there is too much power available
2 / it could damage the amp as load might be disconnected, a tube amp needs loading.

Use a headphone amp, it will also save time on your poweramp as it does not need to be powered on all the time.