It seems the people behind L-type are cheating. All units have the same printed test report ![ThumbsDown :--](https://www.eevblog.com/forum/Smileys/default/icon_thumbsdown.gif)
About a year ago I bought the AD584LH version about a year ago from ebay seller 201377jie. It came with a paper with cal data very similar to the paper discussed in the thread you linked to, with the exception that the voltages were handwritten. I checked it against my HP 3455A and after having the room heated up to 23
oC (like indicated on the cal sheet) and having the meter turned on for about an hour the voltages measured by the HP3455A were surprisingly close to what was on the cal sheet, only a few counts difference at most.
That being said the HP 3455A is really old and hasn't been calibrated for ages, so it might have been just coincidence.
I noticed the AD584LH I got was quite old (date code 0742 - salvaged part?) and seemed to be quite sensitive to temperature; when the room temperature was 15
oC the measured difference was quite a bit larger.
| Cal sheet | HP 3455A (Vin=18.0 V, T=23.5oC ) |
2.5V | 2.50194 | 2.50197 |
5.0V | 5.00326 | 5.00327 |
7.5V | 7.50664 | 7.50666 |
10V | 10.00736 | 10.00736 |