[Boatanchors] Bird 50Ω milspec dummy load measuring @ 56Ω's?

[Howie WA3MCK]

Gang,

I have a Bird 80 watt dummy load, with sealed oil chamber (accessible via
drain plug) and heat radiating fins, that is spec'd at 50Ω.

I have measured the D.C. resistance with several reliable ohm meters at
56Ω. So it's drifted up over the years...

As we used to say in the "Canoe Club" (USN) it's testing "high out of spec"
- a bit over 10%.

Recommendations?
Comments?
Is it on the way out or am I being too picky?

It's been in service here for years. It's never been abused. I have hit it
with about 90 watts on occasion for s few seconds although I doubt that
would have caused the upward drift.

Could use your collective advice!

Thank you de Howie WA3MCK