HP 12C bond calculation

[Randall]

The yield to maturity value from my 12c's do not agree with the brokerage firm, my 17bii+, or financial software running on my 50g.

Any thoughts would be appreciated.

I bought a municipal bond through my brokerage firm:

Settlement date 12/23/2016
Maturity date 2/15/2017
Price 100.628
Coupon 5%
Call 100
30/360 semiannual
Brokerage firm Yield to maturity .637%

I have 2 HP 12c platinum calculators with a single battery. One of them is a 25th anniversary.

Both calculators are set to rpn and show a ytm of .7035%.

I also have a 17Bii+. Using the bond menu it returns a ytm of .63698%.

I also have a 50g using Financial Applications software written by Don Phillips. It returns a ytm of .637%.

Since the 17bii+ and the 50g closely agree with the brokerage firm value I believe them to be correct.

The 12c manual mentions solutions to iterative problems may not exist or there may be multiple roots. I did not see a way to input a starting value.

Or, I may be using the 12c's incorrectly.

Any thoughts as to why the 12c answer does not agree with the others would be much appreciated.

Thanks

Randy