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Pre-A, 356A, 356BT5 Blau Gas Cap ID. Authenticity

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  • Pre-A, 356A, 356BT5 Blau Gas Cap ID. Authenticity

    The Original Blau 100MM Gas cap Remained Virtually identicle and interchangable through the production years 1950-1961. During this eleven year run only few subtle details distinguish one from the other. Such details include: Cadmium to Zinc plating, Cork to later Blue rubbber seal gaskets and Logo changes to the underside of the caps. The following pictures and details will help Identify the Blau gas cap which would most be correct for your particular year and model 356. When these changes were introduced can never be accurately pin-pointed but the following examples will provide a guideline as to which cap your car would have most likely been outfitted with when new.

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    This smooth raised domed center with serrated edges is the standard and remained virtually unchanged through the 11 year production run. The general concensus is they all came silver in color with the early version 1950-1957ish being cadmium plated and later version being Zinc plated. Again there is definitive end as to when the Cadmium was phased out. A combination of both Zinc and Cad plated caps may have been produced in alternating series. I am only going by my most recent knowledge on the subject given to me by long term 356 restorers. If you know of something different please add it. We all want the most accurate info as possible.(example above has been polished and nickle plated)

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    This is the earliest version Blau 100MM Gas cap. Again same baby-moon shape with serrated edges. What distinguishes this cap from a slightly later Pre-A version is the tiny venting hole in the center. This cap is correct and would be found on the very early Non-vented gas tanks from 1950 to only Mid-1951. Vented tanks would be phased in and this tiny hole would no longer be needed. (example above was spray painted black at some point)

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    Known original cap to 1956/57 356AT1 coupe 58367. Again outside shape unchanged. Originally cadmium plated.

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    Known original cap to March 1959 coupe. Unchanged shape. Originally Zinc plated. Photo coutesy of Roy Mawbey.

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    Original 904 Blau 100MM gas cap. Circa: 1965/66 One of the very latest examples of this style cap to be found. Aside from the handle, the body of the cap is identicle to most earliest cap pictured above. Where all these caps really differ in detail is the underside which will be detailed shortly. Thanks for stopping by! Justin
    Justin Rio

  • #2
    The underside details of these Blau caps is what distinguishes them through the 11 year production run.

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    This is the early style logo and would be correct for a Pre-A 356 from 1950 up to 1955ish. Again the exact cut-off point can never really be known. However if you own a Pre-A this would be the most correct version to have for your tank. Small Blau D.R.P. logo with an open loop border and no other markings. This cap would have come Cadmium plated with a cork gasket seal ring. (example above is a known original from a '54 coupe. Some preserved Cadmium plate was found under the original cork gasket)

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    Underside shot of the very early 1950-mid51 vented cap with tiny hole. Same exact logo and detail as the known 1954 example.

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    This is the underside detail of the original cap to 1956/7 356AT1 coupe 58367 and is believed to be the second generation. Same small Blau D.R.P. logo as the known pre-a caps but the words: -OHNE ENTLUFTUNG- have been added to the outer plane. Cap originally had a Cork seal ring and traces of original Cadmium plating under it. Best known information is that this cap style is correct for very early 356A 1956 to late 1957-58ish. Again if you have any further information please post it!
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    Final version of the Blau logo'd cap. D.R.P. name dropped with Blau patent now stamped in its place. Outer details include the dropping of the hyphens and the "ENT" on Luftung on this version. Blue/green rubber seal introduced taking the place of the earlier cork seal. This cap was originally Zinc plated. This is the original cap from Roy Mawbey's March 1959 built 356A coupe. The caps would remain the same on through 356T5 production.

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    Underside detail of the original 904 cap built sometime in 1965-66. Same exact details as Roy's cap from 1959. This leads me to believe that the cap did not change through the 356BT5 production run. But there is always variables. If you have any info to the contrary please post it. Well there you have it; probably more than you ever wanted to know about the evolution of the gas cap but at least you know. Thanks for reading this! Justin
    Justin Rio

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    • #3
      Just wanted to add to the discussion here from a few years back regarding the 100mm Blau gas caps and their markings with regards to their approx issue date. It was stated that the earliest cap was vented and the logo was a small stamping "Blau D.R.P." and bordered by an open loop. The next generation cap was described as identical markings (Blau logo) but no longer vented. But if you look at the two photos of the markings for the first early caps, they aren't identical. One has the open loop border opening up and to the left (10 or 11 o'clock position), and the other opens up and to the right (1 or 2 o'clock position).
      Now I'm not trying to split hairs here, I only bring this up because I have a 100mm Blau cap that has a closed loop border. A 360 degree closed circle, but otherwise the same Blau script with D.R.P. right below, just like the ones shown. This is from a '53 pre-A (vin 51383), though I can't be certain that it is original to the car. I can tell you though, that I've had it since 1967.
      Now maybe all you folks have already been through this, and if so, my apologies. I just today stumbled onto this site, via a TheSamba classified ad, as I recall. And it led me right into this pre-A gas cap discussion. I was unaware of this site till now, but sure am enjoying the new adventure. Thanks a lot to all you here who are providing all this good info.
      I can provide a photo if anyone is interested, but it would have to be sent to someone's smart phone as an attachment to a text message, because I'm far too low-tech to know how to interconnect my phone (that has the photos) with my iPad (that's so old it doesn't have a camera), and with my desktop computer, that's pretty old as well...
      Anyway, thanks again to all. I'm gonna go back to the pages of 356 photos I was perusing just a bit ago, until I started drooling all over my tablet screen. I got a bib on now, so I'll be OK .
      Regards!

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      • #4
        Hello Mike, I'm glad you found us. Thanks for joining and Welcome!

        Nice catch on the loop opening orientation between those early caps; That's detail I missed. So your cap is the same but with a closed loop? I'll be on the look out for that detail in the future. Thank you for the input and Welcome once again!
        Justin
        PS: Nice to read that you're enjoying your visits here so far.
        Justin Rio

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        • #5
          Hi Justin,
          Thanks for the "Welcome", and Yes!, I certainly am enjoying this site. I went through a bunch of great photos last night, then bounced around sorta randomly. Then today was enjoying the first several pages of your $75 Carrera biography. Neat story! And then just now I've noticed that I still have100+ pages to go. Looking forward to that, though.
          So again, thanks for the greeting and thanks to all for all the good info. Gonna be spending a lot of time here....

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          • #6
            My pleasure! Thank you for taking a look through that whole saga.
            Justin
            Justin Rio

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