Reusing Elements in a DTD

I started work where some XML and DTD files were provided to me. They work fine, but I noticed that in DTD they reused such an element.

DTD:

<!ELEMENT image EMPTY>
    <!ATTLIST image 
        source CDATA #REQUIRED
        signature (true|false|1|0) "false" 
    >

and in xml the image element is displayed in two places, but only one of the places requires the attribute 'signature', otherwise it does not matter.

XML:

<root>
  <element-with-optional-signature-image>
     <image source="1.jpg" singature="true" />
     <image source="2.jpg" />
  </element-with-optional-signature-image>
  <other>
     <image source="3.jpg" />
  </other>
</root>

I have never seen a DTD written this way before, and just wondered if this is the usual or really bad way to do this? I would create two different elements element-imageand other-image.

EDIT -

The above is also accepted as a DTD, for example:

<!ELEMENT element-image EMPTY>
    <!ATTLIST element-image 
        source CDATA #REQUIRED
        signature (true|false|1|0) "false" 
    >

<!ELEMENT other-image EMPTY>
    <!ATTLIST image 
        source CDATA #REQUIRED
    >

with XML as follows:

<root>
  <element-with-optional-signature-image>
     <element-image source="1.jpg" singature="true" />
     <element-image source="2.jpg" />
  </element-with-optional-signature-image>
  <other>
     <other-image source="3.jpg" />
  </other>
</root>