By 5 -6A fused extension, the amp does have an internal fuse.  Not sure if this was stock or added by a previous owner.  Depending on where the fuse is in the power path and the value of that fuse, is that an alternative to having to come up with a new dedicated fused extension?  I've got enough power strips laying around, probably makes sense to swap a lower amp breaker into an old strip to give me a ready made go-to for future use

No, I haven't plugged it in yet.  Thanks for the "hot" advice.  I was thinking I'd also pull the tubes before I plug it in to see if anything smoke checks...then try it again with just the rectifier tube and then the preamp, etc.  Based on the condition of the homemade power cord extension, it hasn't been plugged in for some time.  That mess would have popped a breaker or two.

More pics

Okay, more pics and data...
The cap can is an Aerovox, made in New Bedford, Mass.  The company is still in existence.  I've talked to their customer service.  They have no record of this model.  The rest of the components I haven't researched yet.

The fatter orange cap is a Cornell Dublier

The larger wax coated orange cap...I can see some numbers but not a maker name.

The small yellow cap is an Astron.

The thin blue green cap is a "Solar Sealdtite Wax-Molded Paper Capacitor".

The smaller orange wax coated cap is a "Tube - U - Lar Wax-Molded Paper Capacitor" made by Pyramid Electronics.

The preamp tube is a 6SN7GT.

The black transformer has 32 ? - 2 stenciled on it...the third digit is fudged up...could be a 4, could be an A.  Can't see any markings on the small silver xfmr.

The cap can and black xfmr are both electrically connected to a flat brown bar shaped component that's held down by a metal bracket.  The metal bracket is stenciled:
K59J131-5
Res 625

The "Utah" speaker part number is B104759-1

Other than dust, dirt and a very poor attempt at adding an extension to the AC power cord, the entire amp looks to be original. 

The 1948 date may or may not be accurate.  The date came from a vintage guitar equipment dealer located in Amsterdam, Netherlands via a web search.  He knew nothing about the history, manufacturer, etc of this type of amp and had gotten rid of his some time ago.  His listing is apparently trapped in the MATRIX and still shows up via web search.

Sure thing,  I'll update with internal pics hopefully later tonight @ 10 pm EST.  What I remember of the components is the speaker is a "Utah",  made in Huntington, Indiana.  It has a little lightning bolt for a logo.  The rectifier tube is a 7Y4, power tube is a 6V6GT, both are Sylvania brand...can't recall the pre-amp tube number right now.  The tube sockets are made by Admiral.  The tubes don't look to be 60 years old but who knows.

Looking for any info on a Symphony Porto-Amp made in 1948.  Small 3 tube practice amp @ 12" x 12" x 5".  One knob labeled "Volume" and two inputs labeled "Instruments", runs on 110 Vac wall power,  8 inch speaker.

Has a removeable front cover that is covered in it's original fake alligator skin material, back cover is covered in the same material.

Thanks for the help especially about the not precise signal measurements.  I figured there would be some voltage differences given component value drift over the years but it's good the hear it from an outside observer.  Definite cure for potential troubleshooting headaches!

 Looking for some advice concerning injecting a test signal into a fender Princeton Chorus amp.  I have some modest experience troubleshooting electronics but this is my first go at a guitar amp.  The factory schematic calls for a 1 kHZ input signal in order to achieve the signal values listed at the various test points on the schematic.  However the schematic makes no mention of a voltage requirement for the 1 kHZ test signal.  The first test point in the signal flow is "TP9", a tie point right after input jack #1.  The signal value listed is 2 mVAC.  Should this be the value of my 1 kHZ test signal?  My next question is a bit of a newbie no-brainer but I want to be sure...to inject the signal do I just take an old guitar cord jack plug and attach a couple of leads to hook it up to the sig gen and amp?
Attached is a cut of the input for the amp.  Thanks in advance!