EAST ORANGE, N.J. — Locally based brokerage firm Gebroe-Hammer Associates has arranged the $6.8 million sale of a 52-unit apartment building in the Northern New Jersey community of East Orange. The historic building at 60 N. Arlington Ave. offers 30 one-bedroom units, 17 two-bedroom residences and four three-bedroom apartments. David Oropeza of Gebroe-Hammer represented the seller, a limited liability company, in the transaction. Oropeza also procured the buyer, a private investor. Both parties requested anonymity.