What are the these?

[GAD]

Hmm - no sure about the last post...

 

[GAD]

Definitely something related though.

 

[GAD]

This could be it, too:

 

[M-30]

Look what I found!

The box is a Vintage Switchcraft No. 311 Mini Audio Mixer Splitter for Guitar-Harp Mic:

Switchcraft 310, (Vintage) Mini-Mix Audio Mixer, Dual Line Control

NEW Switchcraft 310, Miniature, High Imepdance Microphone Mixers Accommodate 2, High Impedance Inputs with Low Cost Factor. Feeds 2 Signals into a Single Output. This Connector is New Old Stock (N.O.S.) from a bulk case with no retail packaging. The contacts are silver plated and are showing...

marvac.com

Vintage Switchcraft No. 311 Mini Audio Mixer Splitter for Guitar-Harp Mic 1960's | Reverb

This listing is for a vintage Switchcraft No. 311 mini audio mixer/splitter. This mixer/splitter features 2 x Mono 1/4" input jacks and one male 1/4" output plug and 2 thumbwheel knobs to control/balance the volume of each signal. These are great for splitting a guitar signal to 2 amps or balanc...

reverb.com

That's it!The switchcraft 310.
I can't believe you found this.
Too cool!

 

[M-30]

And I think the other is #342 the 'silent plug'.This is great.Ive slways wondered about these.
Thanks for all your help GAD!

 

[Boneman]

That’s awesome sleuthing in less than a few hours, so cool! The gadgets are fascinating stuff. So did they have a mic and a harmonica go through the switchcraft so they would both come out one amp?

 

[M-30]

That’s awesome sleuthing in less than a few hours, so cool! The gadgets are fascinating stuff. So did they have a mic and a harmonica go through the switchcraft so they would both come out one amp?

I think so.Maybe into a recording console?This unit has patent number 310 stamped onto one end.Couldnt get a clear shot of it,but it's there.
Simpler times.
Thanks for identifying these for me.