The original Birmingham proof was 1983 (J & partial B in the circle) at 3 1/4 TONS
After sleeving the London Proof is 1999 at CIP standard proof; Maximum Average (SERVICE) Pressure 740 BAR = 10,733 psi; Maximum Statistical Individual Pressure 850 BAR = 12,328 psi
The original bore was 12 = .729 to .739". The sleeved bore is .736"

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