(a) No vesting service shall be deemed to have accrued prior to June 1, 1968.
(b) After May 31st, 1968, vesting service shall accrue at the rate of one (1) year of vesting service for each Plan year in which a person accrues 870 or more hours and at the rate of one-half (1/2) year of vesting service for each Plan year in which a person accrues less than 870 hours of service but more than 434 hours of service.
(c) Only the following hours of service shall be recognized:
(1) hours of service completed while working in covered employment; and
(2) hours of service completed while not working in covered employment but while working within the geographical jurisdiction of a participating local for a contributing employer.