<p>The drawing is from the 1958 U.S. patent for a rocker-roller <a href="https://en.wikipedia.org/wiki/Balance_board#Rocker-roller_boards" class="extiw" title="en:Balance board">balance board</a> designed by Frederic George Ludwig of Woodbridge, Connecticut.<br>
In the online database of the U.S. Patent and Trademark Office, the version of the patent that includes the application for it that was filed on <a rel="nofollow" class="external text" href="http://patimg1.uspto.gov/.piw?Docid=2829892&amp;idkey=NONE">November 7</a>, 1955 contains more <a rel="nofollow" class="external text" href="http://patimg1.uspto.gov/.piw?PageNum=2&amp;docid=02829892&amp;IDKey=157EDCFDB69F&amp;HomeUrl=http%3A%2F%2Fpimg-piw.uspto.gov%2F">drawings</a> than the <a rel="nofollow" class="external text" href="http://patimg2.uspto.gov/.piw?Docid=02829891&amp;homeurl=http%3A%2F%2Fpatft.uspto.gov%2Fnetacgi%2Fnph-Parser%3FSect1%3DPTO1%2526Sect2%3DHITOFF%2526d%3DPALL%2526p%3D1%2526u%3D%25252Fnetahtml%25252FPTO%25252Fsrchnum.htm%2526r%3D1%2526f%3DG%2526l%3D50%2526s1%3D2,829,891.PN.%2526OS%3DPN%2F2,829,891%2526RS%3DPN%2F2,829,891&amp;PageNum=&amp;Rtype=&amp;SectionNum=&amp;idkey=NONE&amp;Input=View+first+page">June 8</a>, 1955 version does. There are also more descriptions in the <a rel="nofollow" class="external text" href="http://patimg2.uspto.gov/.piw?PageNum=3&amp;docid=02829892&amp;IDKey=157EEDC9B69A&amp;HomeUrl=http%3A%2F%2Fpatft.uspto.gov%2Fnetacgi%2Fnph-Parser%3FSect1%3DPTO2%2526Sect2%3DHITOFF%2526p%3D1%2526u%3D%25252Fnetahtml%25252FPTO%25252Fsearch-adv.htm%2526r%3D1%2526f%3DG%2526l%3D50%2526d%3DPALL%2526S1%3D02829892%2526OS%3DPN%2F02829892%2526RS%3DPN%2F02829892">November</a> version than in the <a rel="nofollow" class="external text" href="http://patimg2.uspto.gov/.piw?docid=02829891&amp;SectionNum=3&amp;IDKey=7A59ECCC466B&amp;HomeUrl=http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1%2526Sect2=HITOFF%2526d=PALL%2526p=1%2526u=%25252Fnetahtml%25252FPTO%25252Fsrchnum.htm%2526r=1%2526f=G%2526l=50%2526s1=2,829,891.PN.%2526OS=PN/2,829,891%2526RS=PN/2,829,891">June</a> version.  
</p><p>The November version's descriptions of the rope are of one that is elastic. <br></p>
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Frederic George Ludwig
1955
<a rel="nofollow" class="external text" href="http://patimg2.uspto.gov/.piw?Docid=02829891&amp;homeurl=http%3A%2F%2Fpatft.uspto.gov%2Fnetacgi%2Fnph-Parser%3FSect1%3DPTO1%2526Sect2%3DHITOFF%2526d%3DPALL%2526p%3D1%2526u%3D%25252Fnetahtml%25252FPTO%25252Fsrchnum.htm%2526r%3D1%2526f%3DG%2526l%3D50%2526s1%3D2,829,891.PN.%2526OS%3DPN%2F2,829,891%2526RS%3DPN%2F2,829,891&amp;PageNum=&amp;Rtype=&amp;SectionNum=&amp;idkey=NONE&amp;Input=View+first+page">Patent 2,829,891</a> of the U.S. Patent and Trademark Office