The Snow White in the poster was the actual cast member at that time who played the princess in the park, and she posed for the painting. In addition, Boyer mentions in the Summer 1987 Disneyana Collector newsletter, that the little girl model is his own grandchild.
For one day only on July 17th, the date of the 1987 theatrical re-release, these posters were given away free to Disneyland guests as they exited the park. The cast members at the gate would ask if you were coming back inside. If you said yes, you didn't get one. If you said no, they gave you a poster.
As mentioned in the earlier post, just outside the gate, the Disneyland Post Office had set up a temporary booth where they were cancelling postage with a commemorative Snow White rubber stamp. Snow White enthusiast Barbara of Harborhousee55 took her free poster over and got it stamped.
Stamped Poster. Image courtesy of Harborhouse55. Used with permission.
Printed at the bottom of the poster are these words...
In honor of the Golden Anniversary of "Snow White and the Seven Dwarfs," Disneyland presents this limited edition commemorative poster by Disney Artist Charles Boyer. July 17, 1987.In fine print...
© 1987 The Walt Disney Company
A similar poster was also made available to Disneyland cast members. The only difference was in the footer text.
Image courtesy of the Kevin Hicks Collection.
Disney Legend recipient Charles Boyer started his career at Disney in 1960 by accepting a "temporary" job at the theme park. He was Disneyland's very first full-time artist and ended up staying for 39 years.
Charles produced nearly fifty collectible lithographs, as well as a diverse range of artwork for magazine covers, brochures, and flyers -- even Company-commissioned oil portraits for retiring employees. He has worked in all media including pastels, oils, watercolors, gouache, acrylics, pencil, and ink. Source: Disney LegendsHe retired in 1999.
Image of Charles via LaughingPlace.com