the job title, you can be a hitman upon completing a job on the hitman job tier. for the achievement you need to take a bounty on the hitlist at least once.
You can get rings on Mafia Wars by doing Hitman jobs.
Exterminate Mafia Rival in the Hitman Tier
The tier that the "Repel the Yakuza" job is in in "Mafia Wars" is the Hitman Tier.
hitman job tier
Hitman Tier - Repel the yakuza.
You can get the ties by doing the jobs under the hitman tier.
Hitman>Assassinate a Political Figure
you do the jobs in the hitman job tier until you get it.
Any of the Hitman tier jobs
u do jobs on the hitman teir list
Hitman Tier in New York
Diamond ring is one of the vault collections you obtain doing jobs on the hitman tier of New York.See related mafia wars wiki link.its a random drop from the hitman tier