如何理解下文中的Those

chen2013

Existing pressure parts that have been stamped and
certified to an earlier or later Edition than those established
for construction of the pressure vessel or part,
and that have never been placed in service (i.e., they were
placed in stock for future use), may be used provided they
are acceptable to the Manufacturer as described in (a).
如何理解文中的Those,欢迎大家发表意见