Open clusters have long been used to illuminate both stellar evolution and Galactic evolution .
The oldest clusters , though rather rare , can reveal the chemical and nucleosynthetic processes early in the history of the Galaxy .
We have studied two turn-off stars in the old , metal-rich open cluster , NGC 6791 .
The Keck + HIRES spectra have a resolution of \sim 45,000 and signal-to-noise ratios of \sim 40 per pixel .
We confirm the high value for [ Fe/H ] finding +0.30 \pm 0.08 , in agreement with earlier results from evolved stars in other parts of the HR diagram .
We have also determined abundances for Na , Si , Ca , Ti , Cr , Ni , Y and Ba .
These are compared to a sample of old , metal-rich field stars .
With the probable exception of enhanced Ni in the cluster stars , the field and cluster stars show similar abundances of the elements .
Model predictions show that the Ni enhancement could result from enrichment of the pre-cluster gas by SN Ia .
Orbital evidence indicates that NGC 6791 could have originated near the inner regions of the Galaxy where the metallicity is generally higher than it is in the disk or halo .
Subsequent perturbations and migrations may have resulted in its current heliocentric distance of 4 kpc and 1 kpc above the Galactic plane .