Galvanized finish on 67-68 tail light housings, hot dipped or electroplated?

[bowtie68iho]

The original 67-68 tail light housing backing plates after almost 50 years look like a dull gray plating with a spangle pattern.  I'd say they almost look like an old galvanized chain link fence that has lost its luster over the years.  Even the repros have duplicated the aged, dull, finish (but the repros don't have the SAE 67 stampings).  Chain link fences are/were hot-dipped galvanized and also have the spangle pattern in the finish due to large zinc crystallites in the molten solution. 

Electrogalvanizing, also known as "clear zinc" plating, is a thinner plating than hot-dipping and does not have the spangle in it. 

In a separate CRG blog under Restoration, "Cadmium vs. Zinc Plating," JohnZ stated that either zinc or cadmium plating was an option in the 60's.  However, he didn't clarify which form of zinc and for which parts.  I'm guessing certain parts were clear zinc and certain ones were hot-dipped?  A good picture of aged, dull looking original ones, is posted under CRG blog Restoration, "Restoring a galvanized finish ."

Does anyone know with certainty whether hot-dipped galvanizing or electrogalvanizing (i.e., "clear zinc"), or either, were original plating finishes on these housing backing plates?  Either finish would be shiny and look very different than the aged, dull look on all original and repro ones today.  It is important for our community to know if either or both of these finishes are acceptable to judges.

Thanks in advance!

[69Z28-RS]

Attached is a photo of the back of a pair of '67 TL housings which came from a race car (long ago take offs) that I think might be representative of 'original'??

[Mike S]

 I checked my '67 04B LOS and '67 05B NOR original tail housings and they have a very clear and definite spangle texture.
I would say they were hot dipped.

Mike

[bowtie68iho]

69Z28-RS,

I noticed Phillip head screws holding the housings onto the bezels.  Are these correct for originality?  I thought the fasteners were hex head zinc screws?

Bernie

[JohnZ]

I'd guess, based on volume economics, that they were stamped from hot-dip galvanized rolled sheet stock, which then required no further processing or handling. 

[Mike S]

 Interesting observation and topic! I checked my housings and found the 05B NOR used Phillip heads on L&R side and the 04B LOS used Phillips on one side and hex heads on the other.
I don't know if it was a NOR vs. LOS thing or a transition from one head type to the other starting around 04B (good idea for a poll?). I doubt it would be one of those 'as long as it fits' usage being the assembler would have to switch out the tool to screw them on.
  I attached images of the NOR and LOS fasteners and a closeup of the hex fastener marking  used on the LOS tail housing.

Mike

[Mike S]

I'd guess, based on volume economics, that they were stamped from hot-dip galvanized rolled sheet stock, which then required no further processing or handling.  

 I agree with that about stamping from stock. I looked at the lamp opening edges and see they are exposed steel with no galvanizing, obviously from the hole stamping process

Mike

[69Z28-RS]

69Z28-RS,

I noticed Phillip head screws holding the housings onto the bezels.  Are these correct for originality?  I thought the fasteners were hex head zinc screws?

Bernie

I bought those from a racer friend, and then sold them.  I know very little about '67's.. and only noted that the taillight housings seemed in very good shape...

[MyRed67]

I'd guess, based on volume economics, that they were stamped from hot-dip galvanized rolled sheet stock, which then required no further processing or handling. 

  I agree with that about stamping from stock. I looked at the lamp opening edges and see they are exposed steel with no galvanizing, obviously from the hole stamping process

Mike

I also agree on this process, as I saw minor surface around the edge of holes.  My 11A  LOS built car has all Phillips screws on both backing plates.

[big iron]

Interesting observation and topic! I checked my housings and found the 05B NOR used Phillip heads on L&R side and the 04B LOS used Phillips on one side and hex heads on the other.
I don't know if it was a NOR vs. LOS thing or a transition from one head type to the other starting around 04B (good idea for a poll?). I doubt it would be one of those 'as long as it fits' usage being the assembler would have to switch out the tool to screw them on.
  I attached images of the NOR and LOS fasteners and a closeup of the hex fastener marking  used on the LOS tail housing.

Mike

My Nor 05E are all hex with G&L head markings.
Bob

[Mike S]

 Looks like there is no pattern for usage between the two different types of fasteners.

John Z. - were the tail lamp housings already assembled from the supplier? If a vendor provides them, who actually would specify the type of fastener head to use?

Thank You,
Mike

[JohnZ]

Looks like there is no pattern for usage between the two different types of fasteners.

John Z. - were the tail lamp housings already assembled from the supplier? If a vendor provides them, who actually would specify the type of fastener head to use?

Thank You,
Mike

The taillights were supplied fully-assembled, ready to install, by Guide Lamp Division, and nobody specified the fastener headmarks - fasteners were specified by part number on the lamp drawing. The fastener part number specified the head type (phillips, hex, etc.), and any vendor that supplied that part number had its own headmark on the screw - NOBODY anywhere in the system paid any attention whatsoever to headmarks - only to part numbers.

[Mike S]

Hi John,

  Thanks for chiming on. By head type I was referring to hex or Phillip. So, somewhere along the lamp units revision history the fastener type was changed. Looking at the small sample below there doesn't seem to be any hint of when the type transitioned. Oh well, still an interesting topic 
So far we have:

Year  Tag date   Plant  Head type
67      11B          LOS   Hex
67      04B          LOS   Hex (L) & Phillip (R)
67      05B          NOR   Phillip (L&R)
67      05E          NOR   Hex   (L&R)
67       ?                ?    Phillip (L&R) - posted by 69z28-rs

Mike

[cook_dw]

67   11E     NOR  Phillip (L&R)
68   03D     NOR  Hex (L&R)

[Mike S]

Thanks Darrell !

Year  Tag date   Plant  Head type
67      11B          LOS   Hex
67      11E          NOR   Phillip (L&R)
67      04B          LOS   Hex (L) & Phillip (R)
67      05B          NOR   Phillip (L&R)
67      05E          NOR   Hex   (L&R)
67       ?                ?    Phillip (L&R) - posted by 69z28-rs
68      03D          NOR   Hex   (L&R)