Only early HJ (& late HQ) was like this, later HJ went to 999,999 km before returning to zero, similar to HX/HZ etc.
I would keep the old speedo for record & if there was a query, you just show whoever is concerned the old speedo & the NOS one.
Fitting & new speedo & staring at zero is not a crime, unless it meant to deceive.
Dr Terry
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