Document Overview:
This technical document appears to be a design specification sheet for a mechanical component named "Big 90 recessed latch FST key". It includes identification codes, material information, weight, dimensions, and notes on assembly and surface treatment.

1. Identification and Metadata:
- Part Number: YLSA90FIK
- Designer: Andrea Angioloni
- Creation Date: 23/09/2015
- Last Revision Date: 11/12/2019
- Weight: 398.26 grams
- Material: Not explicitly specified but indicated as "Th" (possibly shorthand or incomplete)
- Scale: Not specified
- Note: The design is proprietary to YACHT LUXURY STYLE and reproduction or disclosure without authorization is prohibited.

2. General Tolerances and Surface Treatment:
- General tolerances are referenced as "A4" but no detailed values are provided.
- Surface treatment details are not explicitly stated; the document mentions "On Request (MIN 8mm)" which may relate to surface finish or machining requirements.

3. Dimensional and Assembly Specifications:
- The latch features a hexagon key with dimensions 19 mm and 26 mm.
- Support surface on the hatch is specified.
- Fastening includes 4 x M6 screws with 6H tolerance.
- Various dimensions are listed: 66.5 mm, 90 mm, 40 mm, 30 mm, 12.5 mm, 4 mm, 12 mm, 8 mm, and 30 mm, likely corresponding to component features such as length, width, depth, or hole sizes.

4. Functional Notes:
- The grub screw allows adjustment at every point of the stem, enabling clamping of the lever.

Summary of Critical Information:
- Proprietary design for a recessed latch key.
- Precise mechanical dimensions and fastening details provided.
- Adjustable clamping mechanism via grub screw.
- Weight and part identification clearly stated.

This document serves as a technical reference for manufacturing or quality control of the specified latch component, emphasizing proprietary restrictions and mechanical specifications.