[maple_leaf_eh]

I'll have to ask one of the old-time surveyors about aluminum pins. My mind goes towards a year-by-year marker when a job is close to being finished, but needs to be revisited next survey season. For some reason your pin was not retrieved when the job was completed, or the survey parties had worked their way across to the edge of the next map sheet and had no compelling reason to go all the way back for a written-off marker.

Your island should have been collected in one season by a party of three, four, five surveyors. A party chief, an instrument man and any number of fore and backsight men. The more observations the party can take, the quicker things go but a lot depends on what else is happening in other survey programs.

I have a wartime Canadian map sheet in the unit's collection that has a genuine "there be dragons" data void. It is in southwest Ontario in the diagonally settled agricultural ranges and concessions. Almost all of the sheet is complete with the expected level of detail for buildings, roads, bridges and woodlines. Except on one edge there is a stretch where the surveyor collected what he could see from the road, as would have been the extent of his practical limits, very likely using plane table survey. What he couldn't see he didn't draw, leaving along the edge of the sheet a scalloped wave of white paper! Whoever had the job to edge-match the two adjoining sheets either didn't have any more detail or couldn't extrapolate to fill in the void.