Delicate Danish modern butterfly back dining chairs ID  

Please help me with the identification of these chairs as I don't believe I've ever seen anything like them but am sure it is Scandinavian (Danish?) because of the fine detail in the construction which hints at Ostervig.  These darlings are in bad shap but I plan on giving them a full makeover.Any help or direction to point me to would be most appreciated.  They have a stamp with the number 258 on the bottom stretcher. Size is 16" w x 19" d x 33 3/4" h  Thanks in advance for your help! 
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