[nurxhunter]

CON USA USPS Shipped Price Per Pair is $275. 

While there are so many opinions and fake facts on the sonic characteristics of tubes, these here are pretty much on every Top 5 list.  If you are now using Russian new production E88CC or old production (6n23), regardless of the brand or year made, I am fairly certain that you will be impressed on how these sound.  Note this: of all the old stock manufacturers, the sound of Siemens E88CC varies the most dramatically over time and production code.  For example, in 1967, Siemens eliminated the gray elctro-coat from the chrome metal--called 'silver riser' type. This started with the 'A2' production code. Their sound is VERY different.  Much brighter, to the point of shrill, to my ear; however, not awful.  In 1973 or so, starting with 'A6' code, Siemens E88CC sounds like junk to my ear.  Except for Siemens D-getter E88CC (made only in 1959), the A-Phi-1 designation is the gem in the line.  Just saying.  If a review on tube sound does not specifiy two parameters, the review is simply invalid.  Those parameters are:
1. the tubes must be NOS or NOS-testing to a spec of at least 12,000.
2. The production type code and the year made must be specified.
Nothing else matters.  Not the brand (here RCA), not the printing (here in red), not even 'CCA', which only means what is defined below. 

Within the same production type code, the sound of the tube will be remarkably consistent.  All this info holds for EU-made tubes.  USA tube makers did not use production type codes; so only the year made--the date range-- matters.  The type of getter is a time landmark.  D is pre-1960.  Halo is post-1959.  The shape has nothing to do with the sonics, it is only a time landmark. There was a reason for the shape change. Except for Amperex USA, nothing made in USA with respect to 6DJ8 type is worth listening to.  All this info is qualified by: IMHO.  TME.  YMMV.  ISOFIK.  I hope this note was not too boring to read.  Thanks.

And now, for something entirely different, actually relevant information below.

Tested on two calibrated 'reference grade' tube testers, as always.
Clear glass, shiny gold pins, and NOS++ data spec. NOS means NEW old stock. 
RCA branded labels. Etch codes and perfect data indicate they are should be considered CCa.
CCA means:
1) matched triodes within <5%;
2) noise free;
3) gas free;
4) no leaks;
5) hand selected and tested.

Hickok Professionally Refurb and Calibrated TV-10D/U data. I use a reference tube for each test run.
NOS = 12,500 Gm, with the Maximum meter value = 15,000 and minimum considered at 7,500 Gm.
Each tube has the acid-etched type and date code. They both have ZERO GAS values.

A-Phi-1-5K 14,750/14,750 (Made in Munich Nov/1965). 120% of NOS Spec
A-Phi-1-5J 14,750/14,750 (Made in Munich Dec/1965). 120% of NOS Spec

Thus, the MAXIMUM variance is zero, but actually 1-2%, which is the actual precision of the testers. Ultra-Platinum Perfect Match.
A-Phi-1 E88CC type was made only 1962-1965. The later versions post-1968 sound shrill and do not last as long.

They also PEG THE METER ON MY EICO-666 (Devil Tester!) refurb-calibrated Dynamic Emission tester as follows:
>140/>140 and >140/>140 percent; i.e., meter pegging. Zero leakage value. This agrees nicely with the Hickok data.

An EICO value of 140% of NOS-spec is THE HIGHEST NUMBER ON THE METER, WITH NOS BEING 110%-120% and min @ 65%. No inter-electrode leakage (IEL)--and the EICO 666 is known to be as good as the best testers in this regard.The IEL can (not always, though) relate to gas--and the Hickok TV-10D/U confirms Zero gas and top-flight higher-than-NOS-spec values!

I have one other NIB/NOS pair that tests this perfectly, and yet another NIB/NOS pair that virtually does.
3 pairs total, if buyer wants others.  Price is for one NIB/NOS perfect pair. Discounts for multiple purchases.
Auditioned on my EL84 SEP/TS headphone amp (seen in blurred background of last pic) and CJ Classic 60 (lovely EL34 amp, BTW). 
No sonic variances and they sound just perfect and lovely.

Characteristics:  Transparent, holographic, very nice clarity and linear with the right touch of warmth in upper midrange.
Excellent bass--especially midbass, perhaps the tightest midbass of all the NOS tube varieties.

CONUSA Only (no time to deal with International sales right now).  Free USA tracked/insured USPS.
No PP fee.
Per my high feedback under NuRxHunter at ALL sites, you will not be disappointed.

I have many other swell tubes (including G-Phi-1 - Siemens E188CC, which is a unique and special flavor of sound); feel free to ask.