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 Replies: 48 / Views: 8,518 |
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Pillar of the Community
 Canada
2781 Posts |
literally a pocket find...
at first I thought the clerk at the quickie-mart had given me some junk foreign coin as change...
i was right ticked off until I looked at it closer I saw that it was in fact a toonie, went on thinking that maybe all 09's were that design since it was a special year for the coin...
sat in my change jar for a couple of monthes (glad one of the kids didn't get it for lunch money or it would've ended up back at the convenience store) until I had some time over xmas break to do some googling and ended up here with it.
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Moderator
 Canada
10463 Posts |
Quote:
where would I go to have this error confirmed? (or is that even necessary?) I am quite curious about this coin, and to answer your question, it would be extremely helpful to know the composition. I would happily analyze the composition of that coin for you, using a powerful, state-of-the-art benchtop XRF (non-destructive) which is in my lab at work, at no charge. Several members of this site have sent me error coins and miscellaneous items previously, and they can vouch for me as well. Click on the 'email poster' icon above this post, if you want more details. "Discovery follows discovery, each both raising and answering questions, each ending a long search, and each providing the new instruments for a new search." -- J. Robert OppenheimerContent of this post is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License. See: http://creativecommons.org/licenses...0/deed.en_USMy eBay store
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Pillar of the Community
Canada
1984 Posts |
I would 100% vouch for SPP. I would be completely confident mailing him the coin for analysis.
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Valued Member
Canada
118 Posts |
a Bangladeshi 5 Taka piece is Steel and weights 8.17 gr. It is 26.68 MM Dia. Some of the 1996 and all of the 1998 versions are thicker than the previous versions. The shape looks very promising.
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Pillar of the Community
Canada
2781 Posts |
5 taka is steel (magnetic?) or stainless (non)?
this is non-magnetic.
coinscan.com shows a 1994 version at 7.67 g and 1996 at 8.17 g, was there also a 1998 pressing?
thanks
Edited by Wade
12/30/2011 12:50 am
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Valued Member
Canada
118 Posts |
My world coin book says steel and so did a website I visited. No mention of stainless.
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Pillar of the Community
Canada
2428 Posts |
Personally wade, I think you should send it off to SPP-Ottawa.
You have nothing to worry about sending it to him as he is trust worthy!
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Pillar of the Community
Canada
1733 Posts |
The 5 taka was changed to a magnetic version is 2008, prior versions were were non mag stainless.
I don't know if that's what this is because I don't think the mint made any of them. I haven't figured out what else it might be either. Nothing quite fits.
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Valued Member
Canada
241 Posts |
Hi there. I borrowed the following information from the net. It describes the various materials used in the production of stainless steel products. The composition of the final product has a direct affect upon its magnetic properties.
Sending the coin to SPP for analysis is a great offer. Take him up on that as soon as you can!
[ Stainless steels are a very broad group of metals. The name was adopted as a generic term for steel alloys with a minimum of 10.5% chromium. The chromium gives the steel its 'stainless' properties - essentially corrosion resistance. On the surface of the metal, a very thin chromium-rich oxide layer is formed which is inert - i.e. it prevents the steel from rusting. The advantage of stainless steels over plated steels is that, if scratched or damaged, the steel will 'self-repair' as a new oxide layer is formed. In plated steels, scratches in the plate will often lead to corrosion of the steel underneath.
In general, the higher the proportion of chromium, the stronger the corrosion resistance of the steel. In addition to chromium, other metals are added to give the steel particular properties such as strength and malleability. Specifically nickel is used to strengthen the oxide layer.
As for whether they are magnetic, the answer is that it depends. There are several families of stainless steels with different physical properties. A basic stainless steel has a 'ferritic' structure and is magnetic. These are formed from the addition of chromium and can be hardened through the addition of carbon (making them 'martensitic') and are often used in cutlery. However, the most common stainless steels are 'austenitic' - these have a higher chromium content and nickel is also added. It is the nickel which modifies the physical structure of the steel and makes it non-magnetic.
So the answer is yes, the magnetic properties of stainless steel are very dependent on the elements added into the alloy, and specifically the addition of nickel can change the structure from magnetic to non-magnetic. ]
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Pillar of the Community
Canada
1733 Posts |
Austenitic stainless does become magnetic during cold work hardening, it's a known problem. If it's worked while it's hot, it self anneals and this doesn't occur. Specifically it would become magnetic along a bend or work area and form internal lattices (called martensites), where it would also become more brittle. This can be entirely reversed by annealing it with heat between ~1050-1150 C the final heat needed depending on the specific alloy. In conclusion, you cannot necessarily tell the specific alloy of a metal by whether or not it's magnetic since austenitic stainless will become ferro-magnetic depending on the final cold work process. I think the non destructive testing by SPP would nail this down because speculating based on magnetic properties for stainless is not definitive. When referring to the 5 taka coin, the web at large says prior to 2008 it was made of austentic stainless that apparently was NOT work hardened sufficiently to make it magnetic to a normal magnet, post 2008 it was made from a ferrous alloy that was magnetic. Since the coin we have here is not magnetic but holds that general shape and weight that the 5 taka coin has, we are either faced with a phantom planchet from > two years prior to the date on the toonie that made it's way into the bin or... I don't know. The RCM does have a history of making coins for Bangladesh (including the the five taka coin), so it's not a terribly hard stretch to imagine a foreign planchet getting stuck somewhere for a long length of time. Given the evidence at hand, I think member staircase could easily be correct, it's a Five Taka coin and likely an older version of the planchet pre dating the toonie run by some years. |
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Pillar of the Community
 Canada
9871 Posts |
The OP's coin is '99,no waiting required.
Amazing circulation find.
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Pillar of the Community
Canada
1733 Posts |
Crap I thought it said somewhere it was a 2009 twoonie...
Damned eyesight is starting to get to me.
In that case sure how could it not be that planchet.
Not sure about 500 bucks though, a twonie on a german bimetal planchet ICCS certified was selling in the 70 dollar range a bit ago.
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Valued Member
Canada
241 Posts |
Yes, the $500 guesstimate was based on a couple of out-dated sources. It's best to be conservative, that way anything on the high side is strictly a bonus!
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Pillar of the Community
Canada
2781 Posts |
hey staircase, I liked you better at $500 !
if under $100 it will go in the "cool things" box and the kids can fight over it in 40 or 50 years!
the weight still doesn't match the taka (listed @ 8.17g, this coin is 8.55g - seems like a large variance to me?), so going to send it off to SPP-ottawa so he can zap it. will let you all know what comes of it.
thanks again, it's been an adventure
wade
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Rest in Peace
United States
9104 Posts |
 , wade! |
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Replies: 48 / Views: 8,518 |
First Page
Posted 12/29/2011 10:57 pm
