VolvoGirl, julian-herrera-h specifically made mention of a "payroll deduction IRA" which is the term used by the IRS to refer to regular personal IRA contributions made by direct deposit of some portion of one's pay into an IRA in lieu of depositing it into an ordinary savings or checking account; some employers allow pay to be direct-deposited among several accounts. If that's truly the case, it's not associated with any retirement plan of the employer and would not appear in box 12 of the W-2.
Payroll deduction IRAs are somewhat uncommon, though, so it's good to confirm that these contributions do not appear in box 12 of the W-2 before reporting them on the tax return as either deductible or nondeductible traditional IRA contributions.
