One to Watch: Colonial Penn Life Insurance
The back page of the letter mentions that prospects who already have life insurance may be underinsured, and also discusses how "cash value" is built after the first year.
Lastly, making the letter more engaging, it employs icons for the three response mechanisms: BRE, phone and website. It also shows the premium on the back side of the quote form perfed to the bottom of the letter. It even positions the premium like a buckslip often does—as a "useful guide to Social Security."