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The original TMBs were, if I recall, 6-elements in 4 groups.
The TMB look-alikes (most made by Barsta) are usually 5-elements in 3 groups.
The ED eyepieces like the Astrotech Paradigm, Orion Epic-II ED, Telescope Service ED, etc. are probably closer in performance, with 6 elements in 4 groups and pretty good inexpensive eyepieces.
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