There are 8 reales in one Guatemalan peso, so your tiny 1/4 real coin is worth 1/32 of a peso. Collectors, however, will pay more than that value due to the rarity of these coins.
Over the years the design changes slightly, including the addition of 5 stars beneath the wreath on the reverse side.
A worn piece generally commands less than one US dollar from collectors, but better prices are available for better conditions:
worn: less than $1 US dollar approximate catalog value
average circulated: $6
well preserved: $14
fully uncirculated: $30
There are some *good dates* in the series, which are worth a little more than all the other dates as described in the preceding paragraph. These are:
1874: about $10 in average circulated condition
1876: about $20 average circulated
1883: about $25 average circulated
These are retail values collectors may pay. If you want to sell your coin to a dealer, he or she would pay about one-half retail.