Dear Pat,

Thank you for your help and patience.

The presented object appears to be a collection of four letters from the Civil War period by the Union Army Sutler DH Plumb. Besides the letters to his daughter Ada we have one photograph of DH Plumb and an advertisement for his business. This collection was framed in the second half of the 20th century.
This piece is in good condition and there is no serious damage visible in the images provided.
A fair market estimation would be between 100 to 250 USD.
This estimate is based on actual recent past recorded auction sales of comparable items. Retail "asking prices" can be higher and may vary.

With kind regards,
George