Elegant and highly collectible Parker 61 fountain pen from the early production period (circa 1957) made in USA, presented in the desirable turquoise (Surf Green) Lucite body and fitted with a premium “Heirloom” rainbow gold-filled cap. This example stands out for its high-grade cap construction, marked with double hallmarks: “1/7 14K GF” and “1/7 16K GF”, indicating a thicker-than-standard gold-filled layer and the use of different gold alloys. This configuration produces the characteristic multi-tone “rainbow” effect (subtle variations between yellow and rose gold), associated with the upper-tier Parker 61 finishes of the period. The 1/7 gold-filled specification represents a significantly heavier gold layer compared to the more common 1/10 GF used in standard models, reinforcing its positioning within the higher-end range of Parker production. Further consistency with early production examples is found in the presence of original pearl-grey jewels (top and barrel end), rather than later black variants, a detail often associated with the initial manufacturing phase. The barrel also shows a subtle production mark, consistent with early Parker 61 manufacturing examples. The pen retains its original capillary filling system, a hallmark innovation of the Parker 61, here appearing clean and well preserved. Condition is very good to excellent, with bright cap, vivid color retention on the Lucite body, and well-defined imprints and trim. The rainbow effect remains clearly visible under light, enhancing both aesthetic and collectability. A refined mid-century writing instrument combining technical interest, quality materials and enduring design — a fine addition to any Parker collection or a true heirloom-quality piece. Photos form part of the description.