Both tubes appear to have the same date code of SJ (although faint on one) which should put them as being from 1975. The print on these tubes is fragile and will easily rub off, much of the white print has already rubbed off, but the etched identifying number is still clearly visible. Although used, these tubes should still have some decent life left in them and are priced accordingly. The tubes’ test results are displayed in the photos (New 6550 Spec 100% =11,000 Gm). See the photos for physical / cosmetic condition. Notes Regarding Tube Tests. All tubes are tested on an Amplitrex AT-1000 tester in the automatic Fixed Bias Mode (for the most conservative results). Test Results are for a general reference only, and are not a guarantee of performance, nor a guarantee of how they will test on your tester. No real world (audio) performance measurements are taken.

This particular set is the same as the 3-hole military VT-231 version, and tests strong. Special care was taken not to rub off any of the print while testing. The tubes’ test results are displayed in the photos (New 6SN7 Spec 100% = 2,600 Gm). See the photos for physical / cosmetic condition. Notes Regarding Tube Tests. All tubes are tested on an Amplitrex AT-1000 tester in the automatic Fixed Bias Mode (for the most conservative results). Test Results are for a general reference only, and are not a guarantee of performance, nor a guarantee of how they will test on your tester. No real world (audio) performance measurements are taken.