Death's Head: That's an interesting interpretation that's certainly consistent with the fact (based on SM1 and Voices of War) that the Kilrathi weapon was new as of 2654 and still undergoing tests. But don't we then introduce unwanted ambiguity into the KS Manual's service dates generally? For example, is 2628 the service date for the Kilrathi's laser cannon or Confed's; was it the Kilrathi's or Confed's turreted flak cannon that was retired in 2668? (I assume you're not arguing that each side used and retired a given weapon in the same year.)
In addition, the PTC, so named, is Confed's weapon; the Kilrathi called theirs the "atomic proton-accelerator gun" (Voices of War, Timeline--Year 5136).
Finally, at first blush, I would think the term "service date" would not include time spent on field-testing (but I admit I'm not at all familiar with military practices regarding the use of new technologies). In any event, the summary for the particle cannon in the KS Manual suggests that field-testing is not included in a given service date.