39 Mercury Hood latch pictures
 

Trying to photo document and try and get an Idea about changes with 39 Mercury's. Pictured is my "early" 39 Mercury hood latch along with the "later" version of the same part. Would any of you with 39 Mercury's mind sharing which one you have and corresponding engine number?

Re: 39 Mercury Hood latch pictures
 

https://www.fordbarn.com/forum/attac...3&d=1774612025

https://www.fordbarn.com/forum/attac...4&d=1774612025

Re: 39 Mercury Hood latch pictures
 

Robert, I certainly respect your thirst for knowledge.
In this case, I believe any information you gather will prove ambiguous at best.
There are many variables that would make pinpointing when the early latch was replaced by the second "late" latch.
If you could get your hands on the engineering drawings and release dates, that would most likely narrow down the date "window" about as good as I'd expect possible.
When Ford made a release for production, some (all?) assembly plants used up existing stock. Other plants (unless specified otherwise) may have returned their inventory. And there may very well have been other plants that even though directed to return stock, used the parts up anyway.
Also, one must think about which plants were installing which engine / transmission assemblies. So, no exact correlation between latches and serial numbers...

I have witnessed a number of parts, specifically 1940 that were released for production for Job #1. In other words, the very first 1940 to be built. Yet, there are examples of these "Job #1" parts not entering regular production until thousands of cars had already been assembled with earlier designed parts that were designated "not for production".
Was that one assembly plant? Numerous plants? We will never know.

Re: 39 Mercury Hood latch pictures
 

Just like Kube mentioned, the exact date of a change can't be determined for certain for the reasons he mentioned, and I agree completely with his analysis.
If you want to have the official Ford record, then you should request the Engineering Releases for the specific part number of the 1939 latch. If I read the tag from one of your images correctly the part number is 99A-16892 (sorry if I don't have the model number correct, it's out of my knowledge base). You can request the Engineering Release cards for this part number from the Benson Ford Research Library. These cards should describe the official date the parts were released for production and for which models. They should also have dates that changes were made. You can also ask for copies of the Engineering Drawings ($30 each) but the drawings are typically the final version of the part, not the various earlier versions. Realize that for the reasons Kube listed, just having the dates from these cards doesn't mean that the part was used exactly on or from that date, but at least it will give you an indication and some data from which to make some assumptions as assertions as to when a part was actually intended to be used on a vehicle.
Here's a link to the BFRC archives and how ask if Engineering Releases and Engineering Drawings are available for a specific Ford part number:
https://www.thehenryford.org/collect...earch-services